feat(dashboard): add skill autocomplete server-side enumeration and client wiring

- Add SkillsMixin with _enumerate_claude_skills and _enumerate_codex_skills
- Claude: reads ~/.claude/skills/, parses YAML frontmatter for descriptions
- Codex: reads curated cache + ~/.codex/skills/ user directory
- Add /api/skills?agent= endpoint to HttpMixin
- Add fetchSkills() API helper in dashboard
- Wire autocomplete config through Modal -> SessionCard -> SimpleInput
- Add getTriggerInfo() for detecting trigger at valid positions

Closes: bd-3q1, bd-sv1, bd-3eu, bd-g9t, bd-30p, bd-1ba, bd-2n7, bd-3s3

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

dashboard/components/SessionCard.js

@@ -4,8 +4,9 @@ import { formatDuration, getContextUsageSummary } from '../utils/formatting.js';
 import { ChatMessages } from './ChatMessages.js';
 import { QuestionBlock } from './QuestionBlock.js';
 import { SimpleInput } from './SimpleInput.js';
+import { AgentActivityIndicator } from './AgentActivityIndicator.js';
 
-export function SessionCard({ session, onClick, conversation, onFetchConversation, onRespond, onDismiss, enlarged = false }) {
+export function SessionCard({ session, onClick, conversation, onFetchConversation, onRespond, onDismiss, enlarged = false, autocompleteConfig = null }) {
   const hasQuestions = session.pending_questions && session.pending_questions.length > 0;
   const statusMeta = getStatusMeta(session.status);
   const agent = session.agent === 'codex' ? 'codex' : 'claude';
@@ -144,8 +145,10 @@ export function SessionCard({ session, onClick, conversation, onFetchConversatio
         <${ChatMessages} messages=${conversation || []} status=${session.status} limit=${enlarged ? null : 20} />
       </div>
 
-      <!-- Card Footer (Input or Questions) -->
-      <div class="shrink-0 border-t border-selection/70 bg-bg/55 p-4">
+      <!-- Card Footer (Activity + Input/Questions) -->
+      <div class="shrink-0 border-t border-selection/70 bg-bg/55">
+        <${AgentActivityIndicator} session=${session} />
+        <div class="p-4">
         ${hasQuestions ? html`
           <${QuestionBlock}
             questions=${session.pending_questions}
@@ -158,8 +161,10 @@ export function SessionCard({ session, onClick, conversation, onFetchConversatio
             sessionId=${session.session_id}
             status=${session.status}
             onRespond=${onRespond}
+            autocompleteConfig=${autocompleteConfig}
           />
         `}
+        </div>
       </div>
     </div>
   `;