chat: click-to-resume /chat sessions via Claude --resume

Clicking a session in the list loads its transcript (GET /chat/sessions/:id,
parsed from Claude's JSONL into display messages) and continues the actual Claude
session: a resumeSessionId is threaded chat handler -> send-claude-code -> sidecar
-> claude-manager, which passes --resume <uuid> (in-memory session mapping still
takes precedence for live turns). Parser verified against real transcripts.

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

src/servers/api/chat/chat.ts

@@ -1,5 +1,5 @@
 import { createRouter } from '../../create-router';
-import { getClaudeSessionsCwd, listClaudeSessions } from './claude-sessions';
+import { getClaudeSessionsCwd, listClaudeSessions, loadClaudeSession } from './claude-sessions';
 
 export const chatRouter = createRouter();
 
@@ -10,3 +10,11 @@ chatRouter.get('/sessions', (ctx) => {
   const sessions = listClaudeSessions(email, getClaudeSessionsCwd(email));
   return ctx.json({ sessions });
 });
+
+// GET /chat/sessions/:id — one conversation's full transcript, parsed into display-ready messages.
+chatRouter.get('/sessions/:id', (ctx) => {
+  const email = ctx.get('user').email;
+  const detail = loadClaudeSession(email, getClaudeSessionsCwd(email), ctx.req.param('id'));
+  if (!detail) return ctx.text('Not found', 404);
+  return ctx.json(detail);
+});