[BUG] Prompt suggestions silently stopped appearing in Claude Code Desktop (regression in 2.1.229)

### Preflight Checklist

- [x] I have searched existing issues and this hasn't been reported yet (existing prompt-suggestion issues are all feature requests, not this regression)
- [x] This is a single bug report
- [x] I am using the latest version of Claude Code

### What's Wrong?

Prompt suggestions (the suggested next prompt offered in the input field) stopped appearing entirely in Claude Code Desktop on 2026-08-18. There is no error and no user-visible signal — the feature just silently stopped rendering.

Looking at the app bundle, the host resolves this feature purely from a server-side feature gate:

```js
promptSuggestions: t.By(`162211072`)
```

and the session spawn passes that straight through:

```js
promptSuggestions: oe.promptSuggestions ? !0 : void 0
```

So when gate `162211072` evaluates false, the feature disappears and there is no local override: the `promptSuggestionEnabled` setting can only turn the feature *off*, never force it on.

I can't tell from the client side whether this gate was deliberately rolled back or is misevaluating for my account. Either way the behavior change was silent.

### What Should Happen?

Either prompt suggestions keep working, or — if the gate is intentionally off — the state should be discoverable and locally overridable (e.g. `promptSuggestionEnabled: true` able to force it on, rather than only being able to disable).

### Error Messages/Logs

No errors are emitted. The evidence is the absence of the persisted field.

Session records persist the suggestion as a `promptSuggestion` field in the session store. That field was written consistently for months, then stopped abruptly:

- Last session record containing `promptSuggestion`: **2026-08-18 09:58**
- ~22 consecutive sessions since (Aug 18 afternoon through Aug 20): zero occurrences

Engine version timeline from the desktop logs:

```
2026-08-09 22:21 [CCD] Initialized with version 2.1.219
2026-08-18 11:41 [CCD] Initialized with version 2.1.229
2026-08-18 18:11 [CCD] Initialized with version 2.1.234
```

The cutoff falls inside the 2.1.219 -> 2.1.229 window.

Ruled out locally:

- `promptSuggestionEnabled` is absent from all user/project/local settings files, so it defaults to enabled
- No `managed-settings.json` policy file is present on the machine
- A full app restart refreshed the flag cache with a clean feature-flag bootstrap (no 404 on `/edge-api/bootstrap/.../app_start`) and the feature was still absent
- The updater polls hourly and reports no newer version available

### Steps to Reproduce

This is account/gate dependent rather than input dependent, so it may not reproduce for everyone:

1. Run Claude Code Desktop 1.32885.1 (bundled engine 2.1.234) on macOS
2. Complete any turn in any session
3. Observe that no prompt suggestion is offered in the input field
4. Inspect the session store JSON for that session — no `promptSuggestion` field is ever written

To confirm it is gate-driven rather than local configuration: `promptSuggestionEnabled` is unset, and neither a restart nor any settings change restores the feature.

### Is this a regression?

Yes, this worked in a previous version.

### Last Working Version

2.1.219

### Claude Code Version

2.1.234, bundled in Claude Code Desktop 1.32885.1. (Note: `claude --version` on PATH reports a separate, older standalone CLI install; the desktop app runs its own bundled engine, which is the one affected here.)

### Platform

Anthropic API — macOS (Darwin 25.3.0, arm64)

Start with the desktop app bundle references to feature gate 162211072 and the session-store promptSuggestion field described in the report. Compare behavior across engine versions 2.1.219 and 2.1.229+, then determine whether the gate rollout or local override behavior changed. Done means prompt suggestions return or the disabled state and override behavior are explicit and verified.

索引モデルが issue の本文から書いたものです。