fix(web): usable past-conversation list, and search that finds past sessions

Two home-screen reports from @jordan8037310, both about history that is
present but unreachable.

#260 — "Resume Conversation" rendered 4 rows, then a button that appended
every remaining row into a `max-height: 240px` box, so 35 conversations
landed in a four-row scroll well with no ordering or filtering. Rendering
now goes through `_renderHistoryList()` over a cached corpus: 10 rows to
start, Show more/Show less that grows and shrinks the box (the height cap
is class-driven, `.history-list.expanded`), plus a filter box (name,
folder, #case label, prompts), a sort control (recent / name / folder,
pinned rows still first) and a shown-of-total count. A filter implies
expansion, so every match is visible, and the whole header hides as one
unit while a federated search is active. The A-Z sort keys off the same
string the row renders, since most rows are transcript-backed and carry
no session name at all.

#261 — the search box could not match a past project by folder name:
`harvestSources()` built its session corpus from the live in-memory map,
while past sessions come from `/api/sessions/unified` (lifecycle log +
transcript scan). Folding that scan into the request path would have cost
the search its no-filesystem-reads property, so the corpus arrives via a
bounded snapshot instead: `session-history-index.ts` is published as a
side effect of `/api/sessions/unified` (the home screen fetches it on
open, which is the same screen the search box lives on) and rebuilt
fire-and-forget, single-flight and TTL-guarded when a search finds it
stale. A result for a closed session now resumes the conversation rather
than selecting a tab that no longer exists, and is badged RESUME.

The snapshot is stored unscoped with a per-row owner and re-filtered
through canAccessOwned() on read, so multi-user sees exactly what
/api/sessions/unified exposes: own sessions only, host-wide transcript
history admin-only. Live rows are harvested first and win the dedupe.

Verified end-to-end against a real instance with 60 past sessions: cold
process answers its first search without history and its second with it;
folder-name queries return resume targets; clicking one posts the right
resumeSessionId + workingDir.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

test/routes/search-routes.test.ts

@@ -9,12 +9,13 @@
  * (sessions + events) return results. Source data is injected via the mock
  * route context (sessions map, runSummaryTrackers map, attachment history).
  */
-import { describe, it, expect, beforeEach } from 'vitest';
+import { describe, it, expect, beforeEach, afterEach } from 'vitest';
 import Fastify, { type FastifyInstance } from 'fastify';
 import { registerSearchRoutes } from '../../src/web/routes/search-routes.js';
 import { installRouteErrorHandler } from '../../src/web/route-error-handler.js';
 import { createMockRouteContext } from '../mocks/index.js';
 import { RunSummaryTracker } from '../../src/run-summary.js';
+import { resetHistorySessionIndex, setHistorySessionIndex } from '../../src/web/session-history-index.js';
 
 type Ctx = ReturnType<typeof createMockRouteContext>;
 
@@ -206,3 +207,97 @@ describe('GET /api/search — caps & filters', () => {
     expect(types).toEqual(['event']);
   });
 });
+
+// Issue #261: with 3 live sessions and ~35 past ones, searching a past project's
+// folder name matched nothing — the corpus was the live session map alone. Past
+// sessions now arrive from the out-of-band history index snapshot.
+describe('GET /api/search — past sessions (history index)', () => {
+  beforeEach(() => {
+    resetHistorySessionIndex();
+  });
+
+  afterEach(() => {
+    resetHistorySessionIndex();
+    delete process.env.CODEMAN_MULTIUSER;
+  });
+
+  it('matches a past session by folder name with no live session at all', async () => {
+    const { app } = await harness();
+    setHistorySessionIndex([
+      {
+        sessionId: 'cod-9',
+        name: 'w4-needlework',
+        workingDir: '/home/u/projects/needlework',
+        claudeSessionId: 'claude-uuid',
+        timestamp: 1000,
+        live: false,
+      },
+    ]);
+    const res = await app.inject({ method: 'GET', url: '/api/search?q=needlework' });
+    expect(res.statusCode).toBe(200);
+    const body = JSON.parse(res.body);
+    expect(body.data.totalResults).toBe(1);
+    expect(body.data.groups[0].results[0].jumpTo).toMatchObject({
+      kind: 'resume-session',
+      sessionId: 'cod-9',
+      claudeSessionId: 'claude-uuid',
+    });
+  });
+
+  it('does not duplicate a session that is both live and in the snapshot', async () => {
+    const { app } = await harness((ctx) => {
+      ctx.sessions.set(
+        'dup',
+        fakeSession({ id: 'dup', name: 'needle live', workingDir: '/home/u/needle', lastActivityAt: 5 }) as never
+      );
+    });
+    setHistorySessionIndex([
+      { sessionId: 'dup', name: 'needle live', workingDir: '/home/u/needle', timestamp: 5, live: true },
+    ]);
+    const body = JSON.parse((await app.inject({ method: 'GET', url: '/api/search?q=needle' })).body);
+    expect(body.data.totalResults).toBe(1);
+    // The live harvest wins, so the card still switches to the open tab.
+    expect(body.data.groups[0].results[0].jumpTo.kind).toBe('session');
+  });
+
+  it('multi-user: a non-admin sees neither another user’s past session nor unowned host-wide history', async () => {
+    process.env.CODEMAN_MULTIUSER = '1';
+    const app = Fastify({ logger: false });
+    app.addHook('onRequest', async (req) => {
+      (req as unknown as { authUser: unknown }).authUser = { username: 'bob', role: 'user' };
+    });
+    const ctx = createMockRouteContext();
+    ctx.sessions.clear();
+    ctx.runSummaryTrackers.clear();
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    registerSearchRoutes(app, ctx as any);
+    installRouteErrorHandler(app);
+    await app.ready();
+
+    setHistorySessionIndex([
+      {
+        sessionId: 'mine',
+        name: 'needle-bob',
+        workingDir: '/home/u/needle-bob',
+        timestamp: 3,
+        owner: 'bob',
+        live: false,
+      },
+      {
+        sessionId: 'hers',
+        name: 'needle-alice',
+        workingDir: '/home/u/needle-alice',
+        timestamp: 2,
+        owner: 'alice',
+        live: false,
+      },
+      // Host-wide transcript row: no owning session, so admin-only — the same
+      // rule GET /api/sessions/unified applies when it drops history for non-admins.
+      { sessionId: 'hostwide', name: 'needle-host', workingDir: '/srv/needle-host', timestamp: 1, live: false },
+    ]);
+
+    const body = JSON.parse((await app.inject({ method: 'GET', url: '/api/search?q=needle' })).body);
+    expect(body.data.groups[0].results.map((r: { sessionId: string }) => r.sessionId)).toEqual(['mine']);
+    await app.close();
+  });
+});