Release 0.16.0: owner-only invite for per-RFC contribution + discussion (+ #21 Part C Amplitude wiring)

Wave 5 / Track B. Roadmap item #12. Folds in #21 Part C Amplitude
wiring inline (operator ask: "best practices from the very get-go").

RFC owners can invite specific users to one of two per-RFC roles:
contributor (open PRs + join discussion) or discussant (discussion
only). Non-invited users keep the v0.6.0 anonymous-read contract.
The per-RFC write gate layers on top of the existing
require_contributor gate; a super-draft with no owners yet falls
through to the platform-granted contract, preserving the
v0.6.0/v0.7.0/v0.8.0 contracts in their domains.

Backend: migration 018_rfc_invitations.sql (auto-applied — two
tables: rfc_invitations + rfc_collaborators); api_invitations.py
with five endpoints + transactional email; auth.py helpers
(is_rfc_owner / is_rfc_collaborator / can_discuss_rfc /
can_contribute_to_rfc / can_invite_to_rfc); api_discussion +
api_branches + api_prs gate composition; api_admin.py additive
rfc_invitations[] per user. 237 backend tests pass (18 new in
test_rfc_invitations_vertical.py).

Frontend: InvitationsModal.jsx (owner surface), AcceptInvitation.jsx
(/invitations/accept route), api.js helpers, RFCView.jsx
Invitations button, App.jsx route registration.

Amplitude wiring (inline, #21 Part C):
  - INVITATION_SENT from InvitationsModal { rfc_slug, role_in_rfc }
  - INVITATION_ACCEPTED from AcceptInvitation { rfc_slug, role_in_rfc }
  - identify() BEFORE the accept event with properties: invited_at
    (setOnce), last_invited_to_rfc, last_invite_role_in_rfc,
    claim_method: 'rfc-invite'
  - EVENTS taxonomy extended with INVITATION_SENT + INVITATION_ACCEPTED

No new secrets, no new overlay keys, no operator gesture beyond the
v0.15.0 overlay-set + restart. Frontend build verified green.

Subagent ν shipped the feature on feature/v0.16.0-owner-invite
(a51beec). Driver-side integration squash-merged into main,
hand-resolved VERSION + package.json + CHANGELOG (strict-descending
0.16.0 → 0.15.0), and added the inline Amplitude wiring.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/components/InvitationsModal.jsx

@@ -0,0 +1,202 @@
+// InvitationsModal.jsx — v0.16.0 / roadmap item #12.
+//
+// The RFC owner's surface for issuing per-RFC invitations and watching
+// who has accepted. Opens from the RFC view's header strip when the
+// viewer is the RFC's owner (or a platform admin/owner). Non-owner
+// viewers never see the trigger.
+//
+// The modal shows two stacked sections:
+//
+//   1. "Invite someone" — email input + role picker
+//      (contributor | discussant) + Send. The send goes through the
+//      backend's POST /api/rfcs/<slug>/invitations, which both writes
+//      the row and dispatches the email to the invitee. Success
+//      refreshes the list below and clears the input.
+//
+//   2. "Existing invitations" — every invitation (pending +
+//      accepted + revoked + expired) on this RFC, with revoke
+//      buttons on the pending ones. The status of each row is the
+//      effective status (the backend recomputes expired-from-pending
+//      at read time so an unattended cron isn't required).
+//
+// No custom-message field — that belongs to item #16's platform-
+// level surface, not here. No bulk-invite — one email at a time
+// keeps the gesture deliberate.
+
+import { useEffect, useState } from 'react'
+import {
+  createRFCInvitation,
+  listRFCInvitations,
+  revokeRFCInvitation,
+} from '../api'
+import { EVENTS, track } from '../lib/analytics'
+
+const ROLE_OPTIONS = [
+  { value: 'contributor', label: 'Contributor — can open PRs and join discussion' },
+  { value: 'discussant', label: 'Discussant — can join discussion only' },
+]
+
+export default function InvitationsModal({ slug, rfcTitle, onClose }) {
+  const [invitations, setInvitations] = useState(null)
+  const [loadError, setLoadError] = useState(null)
+  const [inviteeEmail, setInviteeEmail] = useState('')
+  const [roleInRFC, setRoleInRFC] = useState('contributor')
+  const [submitting, setSubmitting] = useState(false)
+  const [submitError, setSubmitError] = useState(null)
+  const [submitSuccess, setSubmitSuccess] = useState(null)
+  const [revokingId, setRevokingId] = useState(null)
+
+  async function refresh() {
+    setLoadError(null)
+    try {
+      const r = await listRFCInvitations(slug)
+      setInvitations(r.items || [])
+    } catch (e) {
+      setLoadError(e.message)
+    }
+  }
+
+  useEffect(() => { refresh() /* eslint-disable-line react-hooks/exhaustive-deps */ }, [slug])
+
+  async function handleSend(e) {
+    e.preventDefault()
+    const email = inviteeEmail.trim()
+    if (!email) return
+    setSubmitting(true)
+    setSubmitError(null)
+    setSubmitSuccess(null)
+    try {
+      await createRFCInvitation(slug, { inviteeEmail: email, roleInRFC })
+      // v0.16.0 + #21 Part C — Amplitude wiring. No PII (the email
+      // is the inviter's input, not the invitee's identity in our
+      // analytics; we record the rfc_slug + role_in_rfc so a future
+      // invite→accept correlation has both halves).
+      track(EVENTS.INVITATION_SENT, { rfc_slug: slug, role_in_rfc: roleInRFC })
+      setSubmitSuccess(`Invitation sent to ${email}.`)
+      setInviteeEmail('')
+      await refresh()
+    } catch (err) {
+      setSubmitError(err.message || 'Failed to send invitation.')
+    } finally {
+      setSubmitting(false)
+    }
+  }
+
+  async function handleRevoke(invitationId) {
+    setRevokingId(invitationId)
+    try {
+      await revokeRFCInvitation(slug, invitationId)
+      await refresh()
+    } catch (err) {
+      setSubmitError(err.message || 'Failed to revoke invitation.')
+    } finally {
+      setRevokingId(null)
+    }
+  }
+
+  return (
+    <div className="modal-overlay" onClick={e => { if (e.target === e.currentTarget) onClose() }}>
+      <div className="modal" style={{ maxWidth: 640 }}>
+        <div className="modal-header">
+          <h2>Invitations — {rfcTitle || slug}</h2>
+          <button className="modal-close" onClick={onClose}>×</button>
+        </div>
+        <div className="modal-body">
+          <p style={{ marginTop: 0, color: '#666' }}>
+            Invite people by email to contribute PRs against this RFC or to
+            join its discussion. Anyone with the link can read this RFC;
+            this surface controls who can <em>write</em>.
+          </p>
+
+          <form onSubmit={handleSend} className="invitations-form" style={{ marginTop: 16 }}>
+            <label htmlFor="invitee-email">Invitee email</label>
+            <input
+              id="invitee-email"
+              type="email"
+              value={inviteeEmail}
+              onChange={e => setInviteeEmail(e.target.value)}
+              placeholder="someone@example.com"
+              autoFocus
+              required
+            />
+            <label htmlFor="invitee-role" style={{ marginTop: 10 }}>Role on this RFC</label>
+            <select
+              id="invitee-role"
+              value={roleInRFC}
+              onChange={e => setRoleInRFC(e.target.value)}
+            >
+              {ROLE_OPTIONS.map(opt => (
+                <option key={opt.value} value={opt.value}>{opt.label}</option>
+              ))}
+            </select>
+            <div style={{ marginTop: 12, display: 'flex', gap: 8, alignItems: 'center' }}>
+              <button type="submit" className="btn-primary" disabled={submitting}>
+                {submitting ? 'Sending…' : 'Send invitation'}
+              </button>
+              {submitError && <span style={{ color: '#c33' }}>{submitError}</span>}
+              {submitSuccess && <span style={{ color: '#383' }}>{submitSuccess}</span>}
+            </div>
+          </form>
+
+          <hr style={{ margin: '20px 0' }} />
+
+          <h3 style={{ margin: '0 0 8px' }}>Existing invitations</h3>
+          {loadError && <div className="error-banner">{loadError}</div>}
+          {invitations === null && <div>Loading…</div>}
+          {invitations !== null && invitations.length === 0 && (
+            <div style={{ color: '#666' }}>No invitations have been sent yet.</div>
+          )}
+          {invitations !== null && invitations.length > 0 && (
+            <table style={{ width: '100%', borderCollapse: 'collapse' }}>
+              <thead>
+                <tr>
+                  <th style={{ textAlign: 'left', padding: 4 }}>Email</th>
+                  <th style={{ textAlign: 'left', padding: 4 }}>Role</th>
+                  <th style={{ textAlign: 'left', padding: 4 }}>Status</th>
+                  <th style={{ textAlign: 'left', padding: 4 }}>Sent</th>
+                  <th style={{ padding: 4 }}></th>
+                </tr>
+              </thead>
+              <tbody>
+                {invitations.map(inv => (
+                  <tr key={inv.id} style={{ borderTop: '1px solid #eee' }}>
+                    <td style={{ padding: 4 }}>{inv.invitee_email}</td>
+                    <td style={{ padding: 4 }}>{inv.role_in_rfc}</td>
+                    <td style={{ padding: 4 }}>
+                      <span className={`invitation-status status-${inv.status}`}>
+                        {inv.status}
+                      </span>
+                      {inv.status === 'accepted' && inv.accepted_by_display && (
+                        <span style={{ color: '#666', marginLeft: 6 }}>
+                          by {inv.accepted_by_display}
+                        </span>
+                      )}
+                    </td>
+                    <td style={{ padding: 4, color: '#666' }}>
+                      {inv.created_at?.slice(0, 10) || ''}
+                    </td>
+                    <td style={{ padding: 4, textAlign: 'right' }}>
+                      {inv.status === 'pending' && (
+                        <button
+                          type="button"
+                          className="btn-link"
+                          onClick={() => handleRevoke(inv.id)}
+                          disabled={revokingId === inv.id}
+                        >
+                          {revokingId === inv.id ? 'Revoking…' : 'Revoke'}
+                        </button>
+                      )}
+                    </td>
+                  </tr>
+                ))}
+              </tbody>
+            </table>
+          )}
+        </div>
+        <div className="modal-footer">
+          <button type="button" className="btn-link" onClick={onClose}>Close</button>
+        </div>
+      </div>
+    </div>
+  )
+}