v0.21.0 header+inbox UX (#24,#25,#31): rename About→Philosophy, inline-SVG inbox icon, light inbox pass

- #24: header link "About" → "Philosophy" (route/title unchanged).
- #25 icon: replace 📮 emoji with a dependency-free inline-SVG envelope
  in .inbox-trigger; aria-label/title reframed to "Inbox". Badge intact.
- #25 inbox UX (light, no redesign): sharper unread/read distinction
  (accent dot + left bar + tint via tokens), per-row "mark as read"
  affordance that marks-without-navigating, clearer "Mark all read"
  label, and a real empty/caught-up state. New Inbox.css is tokenized
  and written one notch more specific than App.css where it overrides
  (Inbox.css injects before App.css under ESM eval order). Data flow,
  API calls, routing-on-click, and badge behavior preserved.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/components/Inbox.jsx

@@ -15,6 +15,7 @@ import {
   markNotificationRead,
   markNotificationsReadByFilter,
 } from '../api.js'
+import './Inbox.css'
 
 const CATEGORIES = [
   { value: '', label: 'All categories' },
@@ -56,11 +57,15 @@ export default function Inbox({ onClose, lastChangeTick }) {
     return Array.from(seen.entries())
   }, [items])
 
+  async function markOneRead(item) {
+    if (item.read_at) return
+    await markNotificationRead(item.id)
+    setItems(prev => prev.map(p => p.id === item.id ? { ...p, read_at: new Date().toISOString() } : p))
+    setUnreadCount(c => Math.max(0, c - 1))
+  }
+
   async function handleRowClick(item) {
-    if (!item.read_at) {
-      await markNotificationRead(item.id)
-      setItems(prev => prev.map(p => p.id === item.id ? { ...p, read_at: new Date().toISOString() } : p))
-    }
+    await markOneRead(item)
   }
 
   async function markAllUnderFilter() {
@@ -121,22 +126,36 @@ export default function Inbox({ onClose, lastChangeTick }) {
           </label>
 
           <button
-            className="btn-link"
+            className="btn-link inbox-mark-all"
             onClick={markAllUnderFilter}
             disabled={items.every(i => i.read_at)}
+            title="Mark every notification matching the current filter as read"
           >
-            Mark all read (under filter)
+            Mark all read
           </button>
         </div>
 
         <div className="inbox-body">
-          {loading && <p className="muted">Loading…</p>}
+          {loading && <p className="inbox-state muted">Loading your inbox…</p>}
           {!loading && items.length === 0 && (
-            <p className="muted">No notifications match. Try a different filter, or come back later.</p>
+            <div className="inbox-empty">
+              <p className="inbox-empty-title">You're all caught up.</p>
+              <p className="muted">
+                {filters.unread || filters.rfcSlug || filters.category
+                  ? 'Nothing matches the current filters. Clear them to see everything.'
+                  : 'New activity on RFCs you follow will show up here.'}
+              </p>
+            </div>
           )}
           <ul className="inbox-list">
             {items.map(item => (
-              <InboxRow key={item.id} item={item} onClick={handleRowClick} onClose={onClose} />
+              <InboxRow
+                key={item.id}
+                item={item}
+                onClick={handleRowClick}
+                onMarkRead={markOneRead}
+                onClose={onClose}
+              />
             ))}
           </ul>
         </div>
@@ -145,16 +164,24 @@ export default function Inbox({ onClose, lastChangeTick }) {
   )
 }
 
-function InboxRow({ item, onClick, onClose }) {
+function InboxRow({ item, onClick, onMarkRead, onClose }) {
   const unread = !item.read_at
   const target = deepLink(item)
   const handle = async () => {
     await onClick(item)
     if (target) onClose?.()
   }
+  const handleMarkRead = async (e) => {
+    // Don't let the row's Link fire — this affordance only marks read,
+    // it never navigates.
+    e.preventDefault()
+    e.stopPropagation()
+    await onMarkRead(item)
+  }
   return (
-    <li className={`inbox-row ${unread ? 'unread' : ''}`}>
+    <li className={`inbox-row ${unread ? 'unread' : 'read'}`}>
       <Link to={target || '#'} onClick={handle} className="inbox-row-link">
+        <span className="inbox-unread-dot" aria-hidden />
         <span className={`inbox-cat cat-${item.category || 'unknown'}`}>{item.category || '·'}</span>
         <span className="inbox-summary">{item.summary}</span>
         {item.bundled_count > 1 && (
@@ -162,6 +189,24 @@ function InboxRow({ item, onClick, onClose }) {
         )}
         <span className="inbox-when">{formatWhen(item.created_at)}</span>
       </Link>
+      {unread && (
+        <button
+          type="button"
+          className="inbox-row-dismiss"
+          onClick={handleMarkRead}
+          aria-label="Mark as read"
+          title="Mark as read"
+        >
+          {/* check glyph — dependency-free inline SVG */}
+          <svg
+            width="14" height="14" viewBox="0 0 24 24"
+            fill="none" stroke="currentColor" strokeWidth="2.25"
+            strokeLinecap="round" strokeLinejoin="round" aria-hidden
+          >
+            <path d="m5 13 4 4 10-11" />
+          </svg>
+        </button>
+      )}
     </li>
   )
 }