§13: make graduation's RFC number optional; add retire (soft delete)

Optional number (§13.2/§13.3): GraduateBody.rfc_id is now optional.
A blank/absent id graduates to `active` with `id: null`, leaving the
slug as the canonical identifier (§2.3). /graduate/check treats a blank
id as valid (ok:true); /graduate only validates the RFC-NNNN regex +
collision check when a number is supplied. The Graduate dialog allows an
empty number and renders number-less entries by slug (no RFC-undefined).

Retire (§3, §3.1, §13.7): new `retired` soft-delete state. An RFC's own
owners (frontmatter) and site `owner`-role holders — not app admins —
retire via POST /api/rfcs/<slug>/retire, an auto-merged meta-repo flip
PR (graduation machinery reused). Retired entries leave every browsing
surface: catalog, get_rfc (404 except site owner), discussion/branch
reads. Un-retire is site-owner-only (POST .../unretire), discoverable
via the owner-gated GET /api/admin/retired-rfcs ("Retired" admin tab).
Migration 025 widens the cached_rfcs.state CHECK to include 'retired'
(table rebuild, all columns preserved).

Tests: graduation no-number cases (active+null id by slug; check accepts
blank) added to test_graduation_vertical.py; new test_retire_vertical.py
covers perms (owner/site-owner allowed, admin/contributor 403),
catalog/read exclusion, and a graduate→retire→unretire round-trip. Full
backend suite 386 passing; frontend builds clean. SPEC §3/§3.1/§13
updated; CHANGELOG + VERSION → 0.33.0.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/components/GraduateDialog.jsx

@@ -109,20 +109,25 @@ export default function GraduateDialog({ slug, entry, onClose, onCompleted }) {
             <p className="modal-intro">
               §13: graduate the super-draft to active. This is an in-place
               state flip — the entry keeps its body and stays in the meta
-              repo; only the frontmatter changes (state, integer ID, and the
-              graduation stamps). No new repository is created.
+              repo; only the frontmatter changes (state, the optional
+              integer ID, and the graduation stamps). No new repository is
+              created.
             </p>
 
             <div className="form-row">
-              <label>Integer ID</label>
+              <label>Integer ID <span className="field-optional">(optional)</span></label>
               <input
                 type="text"
                 value={rfcId}
                 onChange={(e) => setRfcId(e.target.value.trim())}
-                placeholder="RFC-NNNN"
+                placeholder="RFC-NNNN — or leave blank"
                 disabled={phase !== 'idle'}
               />
-              <p className="field-help">Pre-filled as the next free integer; editable to reserve gaps.</p>
+              <p className="field-help">
+                Pre-filled as the next free integer; editable to reserve gaps,
+                or <strong>clear it to graduate without a number</strong> — the
+                slug stays the canonical identifier.
+              </p>
               {idError && <p className="field-error">{idError}</p>}
             </div>
 
@@ -186,8 +191,10 @@ export default function GraduateDialog({ slug, entry, onClose, onCompleted }) {
               <div className="graduation-complete">
                 <h3>Graduation complete</h3>
                 <p>
-                  `{slug}` is now active as <strong>{streamState?.rfc_id}</strong>.
-                  The catalog and the RFC view reflect the new state.
+                  {streamState?.rfc_id
+                    ? <>`{slug}` is now active as <strong>{streamState.rfc_id}</strong>.</>
+                    : <>`{slug}` is now active (no number — identified by its slug).</>}
+                  {' '}The catalog and the RFC view reflect the new state.
                 </p>
               </div>
             )}