[Test Regression] browse/test/sidebar-ux.test.ts — 73 failures on main (pickSidebarModel / ANALYSIS_WORDS missing)

## Summary

Running `bun test browse/test/sidebar-ux.test.ts` on the current `main` branch (`a5833c41` — v1.57.10.0) produces **73 failures and 4 errors** out of 176 tests.

## Reproduction

```bash
git checkout main # a5833c41
bun test browse/test/sidebar-ux.test.ts
# → 103 pass, 73 fail, 4 errors
```

Confirmed on macOS (Apple Silicon). These failures exist on `upstream/main` before any branch changes are applied.

## Failure clusters

**1. `pickSidebarModel` routing**
```
error: expect(received).toBeGreaterThan(expected)
Expected: > 0 Received: -1

at sidebar-ux.test.ts:1665 — routerFn.indexOf('ANALYSIS_WORDS')
```
The test extracts `pickSidebarModel` from `server.ts` and checks the source contains `ANALYSIS_WORDS` / `ACTION_PATTERNS`. Both are absent from the current output — `indexOf` returns -1.

**2. LLM-based cleanup prompts** — 4 tests fail

**3. Sidebar arrow hint / tool_use collapse / idle timeout / shutdown** — ~15 tests fail

## Suspected cause

The Codex review default-on PR (#1966, v1.57.10.0) likely refactored or inlined `ANALYSIS_WORDS` / `ACTION_PATTERNS` in `browse/src/server.ts`. Tests at lines 1651–1690 still expect those symbol names to appear literally in the extracted function source.

## Impact

- `bun test` gives a dirty run on main — blocks contributors from knowing if their PR introduced new failures
- Makes it hard to bisect regressions

## Ask

1. Confirm if this is already tracked
2. If the refactor was intentional — update tests to match the new structure
3. If not — restore the constants or fix the extraction logic

Happy to send a patch once the fix direction is confirmed.