fix: date a working row by its turn, not by the session age

`TuiSessionRow` declared `lastSubmitAt`/`inputTokens`/`outputTokens`,
`stateSince()` ordered the WORKING group by the first of them and
`renderRowLines()` painted the other two, but nothing ever filled any of
them in: the unified list carries none, and the `session:updated` payload
that does was discarded (an event only schedules a refetch).

So a running turn was dated by its SESSION's creation instead. Measured
against the live server before the fix: w65 (created 21h ago, turn started
one minute earlier) outranked w67 (created 15 minutes ago, turn started
five minutes earlier), the reverse of the rule docs/tui.md states, and the
elapsed column read `21h` for a turn a minute old. The token column was
unreachable code for the same reason.

`fetchLiveSessionMetrics()` reads the three fields from `GET /api/sessions`
and `applyLiveMetrics()` folds them onto the rows. That route answers from
the server's cached LIGHT state (no terminal buffers): 10-20ms measured,
against the ~550ms the unified list in the same `Promise.all` already
costs, so it is cheap enough to ride every refresh. It is best-effort like
the approvals and tmux reads beside it, because losing the anchor is
better than losing the list.

A ZERO is treated as unknown rather than merged: `stateSince()` reads
`lastSubmitAt ?? createdAt` and 0 is not nullish, so a merged 0 would date
every never-submitted session to the epoch.

The snapshot path gets the same merge, or `codeman tui --list` would number
the WORKING group differently from the dashboard that `codeman tui <n>`
indexes into.

Verified live: working rows now show 28m/8m (turn age, tokens 280.5k/65.2k)
where they showed 21h/34m and no tokens. The e2e assertion fails on master's
wiring with `[*] 10m` against a session that pressed Enter one minute ago.

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

test/tui/tui-app.test.ts

@@ -11,6 +11,7 @@
  */
 import { describe, it, expect } from 'vitest';
 import {
+  applyLiveMetrics,
   applyMuxNames,
   buildListLines,
   confirmAccepts,
@@ -27,9 +28,9 @@ import {
   tmuxRowsToSessions,
   tmuxSocketFromEnv,
 } from '../../src/tui/tui-app.js';
-import { createTuiModel } from '../../src/tui/tui-model.js';
+import { createTuiModel, stateSince } from '../../src/tui/tui-model.js';
 import { glyphsFor } from '../../src/tui/tui-render.js';
-import type { TuiTmuxSession } from '../../src/tui/tui-client.js';
+import type { TuiLiveSessionMetrics, TuiTmuxSession } from '../../src/tui/tui-client.js';
 import type { TuiConfirmState, TuiRow, TuiSessionRow } from '../../src/tui/tui-types.js';
 
 const GLYPHS = glyphsFor('unicode');
@@ -339,6 +340,66 @@ describe('applyMuxNames', () => {
   });
 });
 
+describe('applyLiveMetrics', () => {
+  const metrics: TuiLiveSessionMetrics[] = [
+    { sessionId: 'aaaa1111', lastSubmitAt: 5_000, inputTokens: 900, outputTokens: 100 },
+    { sessionId: 'bbbb2222', lastSubmitAt: 0, inputTokens: 0, outputTokens: 0 },
+  ];
+
+  it('folds the turn stamp and the token totals onto the matching row', () => {
+    const rows = applyLiveMetrics(
+      [
+        { sessionId: 'aaaa1111', sources: ['live'] },
+        { sessionId: 'cccc3333', sources: ['live'] },
+      ],
+      metrics
+    );
+    expect(rows[0]).toMatchObject({ lastSubmitAt: 5_000, inputTokens: 900, outputTokens: 100 });
+    // No live counterpart (a history row): nothing to fold, nothing invented.
+    expect(rows[1].lastSubmitAt).toBeUndefined();
+    expect(rows[1].inputTokens).toBeUndefined();
+  });
+
+  it('treats a zero as unknown, so a never-submitted session is not dated to the epoch', () => {
+    const [merged] = applyLiveMetrics([{ sessionId: 'bbbb2222', sources: ['live'], createdAt: 1_000 }], metrics);
+    expect(merged.lastSubmitAt).toBeUndefined();
+    expect(merged.inputTokens).toBeUndefined();
+    expect(stateSince('working', merged)).toBe(1_000);
+  });
+
+  it('copies rather than mutating its input, and survives an empty metrics list', () => {
+    const input: TuiSessionRow[] = [{ sessionId: 'aaaa1111', sources: ['live'] }];
+    const rows = applyLiveMetrics(input, []);
+    expect(rows[0]).not.toBe(input[0]);
+    expect(rows[0].lastSubmitAt).toBeUndefined();
+    expect(input[0].lastSubmitAt).toBeUndefined();
+  });
+
+  it('orders the WORKING group by when the turn started, not by session age', () => {
+    // The regression this merge exists for: `old` was created a day before
+    // `fresh` but started its turn a minute AFTER it, so `fresh` has been
+    // working longer and has to lead. Without the merge both fall back to
+    // createdAt and `old` wins.
+    const unified: TuiSessionRow[] = [
+      { sessionId: 'old00000', name: 'old', sources: ['live'], isWorking: true, createdAt: 1_000 },
+      { sessionId: 'fresh000', name: 'fresh', sources: ['live'], isWorking: true, createdAt: 500_000 },
+    ];
+    const turns: TuiLiveSessionMetrics[] = [
+      { sessionId: 'old00000', lastSubmitAt: 900_000 },
+      { sessionId: 'fresh000', lastSubmitAt: 600_000 },
+    ];
+
+    const before = createTuiModel();
+    before.replaceSessions(unified);
+    expect(before.rows().map((r) => r.session.name)).toEqual(['old', 'fresh']);
+
+    const after = createTuiModel();
+    after.replaceSessions(applyLiveMetrics(unified, turns));
+    expect(after.rows().map((r) => r.session.name)).toEqual(['fresh', 'old']);
+    expect(after.rows()[0].since).toBe(600_000);
+  });
+});
+
 describe('buildListLines', () => {
   it('numbers rows in the dashboard order, so `tui <n>` and `tui --list` agree', () => {
     const model = createTuiModel();

test/tui/tui-client.test.ts

@@ -63,6 +63,17 @@ const defaultResponder: Responder = (req, res) => {
       data: { sessions: [{ sessionId: 'abc', name: 'w1-codeman', sources: ['live'] }], total: 1 },
     });
   }
+  if (url === '/api/sessions' || url.startsWith('/api/sessions?')) {
+    // The light state, plus the two rows the narrowing has to discard.
+    return sendJson(res, 200, {
+      success: true,
+      data: [
+        { id: 'abc', lastSubmitAt: 4000, inputTokens: 900, outputTokens: 100, status: 'busy' },
+        { id: '', lastSubmitAt: 7000 },
+        { id: 'zzz', lastSubmitAt: '5', inputTokens: null },
+      ],
+    });
+  }
   if (url.startsWith('/api/approvals')) {
     return sendJson(res, 200, {
       success: true,
@@ -318,6 +329,23 @@ describe('TuiClient remaining API surface', () => {
     expect(recorded[0].url).toBe('/api/sessions/abc/terminal?tail=4096');
   });
 
+  it('reads the turn stamp and token counters off the light session state', async () => {
+    const metrics = await client().fetchLiveSessionMetrics();
+    expect(recorded[0].url).toBe('/api/sessions');
+    // Narrowed to the three fields, keyed by id: a row with no usable id is
+    // dropped rather than folded in under an empty key, and a field of the
+    // wrong type is left absent rather than merged as a string.
+    expect(metrics).toEqual([
+      { sessionId: 'abc', lastSubmitAt: 4000, inputTokens: 900, outputTokens: 100 },
+      { sessionId: 'zzz' },
+    ]);
+  });
+
+  it('reports an unreadable session list as empty rather than throwing', async () => {
+    responder = (_req, res) => sendJson(res, 200, { success: true, data: { sessions: 'not an array' } });
+    await expect(client().fetchLiveSessionMetrics()).resolves.toEqual([]);
+  });
+
   it('starts sessions through quick-start', async () => {
     const result = await client().quickStart({ caseName: 'x', mode: 'claude', parentSessionId: 'abc' });
     expect(result.sessionId).toBe('new-1');

test/tui/tui-e2e.test.ts

@@ -53,6 +53,13 @@ let sessions: UnifiedSessionItem[] = [];
 let approvals: ApprovalItem[] = [];
 /** Terminal buffers the preview pane polls, by session id. */
 const terminals = new Map<string, string>();
+/**
+ * The LIGHT session state (`GET /api/sessions`), which is where the turn stamp
+ * and the token counters come from: the unified list carries neither, so w2-beta
+ * is deliberately a session created 10 minutes ago whose turn started one minute
+ * ago. A row dated by the wrong one of those reads `10m` instead of `1m`.
+ */
+let liveState: Array<Record<string, unknown>> = [];
 /** Everything the TUI posted, so a test can assert on the exact body. */
 const answered: Array<{ id: string; body: Record<string, unknown> }> = [];
 const inputs: Array<{ sessionId: string; body: Record<string, unknown> }> = [];
@@ -184,6 +191,10 @@ function resetSessions(): void {
       lastActivityAt: NOW - 3_600_000,
     },
   ];
+  liveState = [
+    { id: BETA, status: 'busy', lastSubmitAt: NOW - 60_000, inputTokens: 42_000, outputTokens: 3_200 },
+    { id: ALPHA, status: 'idle', lastSubmitAt: NOW - 60_000 },
+  ];
 }
 
 let server: http.Server;
@@ -264,6 +275,9 @@ beforeAll(async () => {
       return sendJson(res, { success: true, data: { version: '9.9.9', planUsage: PLAN_USAGE } });
     }
     if (url.startsWith('/api/sessions/unified')) return sendJson(res, { success: true, data: { sessions } });
+    if (url === '/api/sessions' || url.startsWith('/api/sessions?')) {
+      return sendJson(res, { success: true, data: liveState });
+    }
 
     const previewFor = sessionRoute(url, 'terminal');
     if (previewFor) {
@@ -424,6 +438,17 @@ describe('codeman tui (under a pty)', () => {
     expect(index('RECENT')).toBeLessThan(index('w3-gamma'));
   });
 
+  it('dates a working row by its turn, not by the session age', () => {
+    // w2-beta was created 10 minutes ago and pressed Enter one minute ago, and
+    // only `GET /api/sessions` knows the second number. `1m` proves the merge
+    // ran end to end; `10m` would mean the row fell back to createdAt.
+    const beta = rowFor(output, 'w2-beta');
+    expect(beta).toMatch(/\b1m\b/);
+    expect(beta).not.toMatch(/\b10m\b/);
+    // The token column rides the same read.
+    expect(beta).toContain('45.2k');
+  });
+
   it('shows the header facts and only the keys that work', () => {
     const lines = frameLines(output);
     expect(lines[0]).toContain('codeman');