Weak assertion in timeline e2e test always passes regardless of nav controls

Summary

The navigation controls visible assertion in tests/e2e/timeline.spec.ts is effectively a no-op — it passes even when the navigation controls are missing.

test(''navigation controls visible'', async ({ page }) => {
  // Should have prev/next day navigation
  const content = await page.textContent(''#content'');
  expect(content).toMatch(/May|2026|prev|next|←|→/i);
});

Why it''s broken

The regex is an OR of six alternatives, and the timeline view always renders text that satisfies at least one branch regardless of navigation state:

1. The CSS class session-preview (rendered for every session row in src/webview/page-timeline.ts around line 246) contains the substring prev, which matches /prev/i against textContent. Even if no nav buttons rendered, the assertion would pass as long as any session row exists.
2. The May / 2026 branches are fixture-bound (they come from tl.date formatted via toLocaleDateString in page-timeline.ts:98), so regenerating the fixture to a different month/year silently kills those branches without anyone noticing — because the prev branch already always matches.
3. Net effect: the test does not actually verify that the prev/next navigation controls are visible. A regression that removes the nav buttons would not fail this test.

Related

Surfaced while reviewing #88, which fixed a similar (but stronger) time-bomb assertion in burndown.spec.ts. This one is weaker but more insidious because it silently always passes rather than failing on a known date.

Suggested fix

Assert the navigation controls directly instead of pattern-matching free text, e.g.:

test(''navigation controls visible'', async ({ page }) => {
  await expect(page.locator(''button:has-text("Prev")'')).toBeVisible();
  await expect(page.locator(''button:has-text("Next")'')).toBeVisible();
});

Or target whatever stable selector / data-testid the prev/next controls expose in the timeline page.

Acceptance criteria

• tests/e2e/timeline.spec.ts navigation controls visible asserts on the actual prev/next nav controls (locator/selector based), not a free-text regex.
• Removing or hiding the prev/next nav buttons in src/webview/page-timeline.ts causes the test to fail.
• No hard-coded month/year strings remain in the assertion.