fix(hooks): record_hook_timing and HookTimer are defined but never called — hook timing stats are dead code

[JeremyDev87]

Problem

The CodingBuddy plugin has two hook-timing facilities — both fully implemented, both fully tested, both never invoked by any actual hook. As a result:

1. The Stop hook summary never shows the `⏱ PreToolUse:Xms PostToolUse:Yms` timing report that `SessionStats.format_summary()` is wired to emit.
2. Every `PostToolUse` / `PreToolUse` / `SessionStart` / `Stop` script runs without measuring its own runtime, so the project has zero data on hook performance even though the data structures exist.

Affected code

Facility 1 — `SessionStats.record_hook_timing`

File: `packages/claude-code-plugin/hooks/lib/stats.py`

```python
def record_hook_timing(self, hook_name: str, elapsed_ms: float) -> None:
"""Record a hook execution timing in memory."""
if hook_name not in self._mem_hook_timings:
self._mem_hook_timings[hook_name] = []
self._mem_hook_timings[hook_name].append(elapsed_ms)
self._pending_count += 1
```

Search proves this method is never called by hook code:

```bash
cd packages/claude-code-plugin
rg -n 'record_hook_timing' hooks/

Only match: hooks/lib/stats.py — the definition itself.

```

`format_summary()` already consumes `hook_timings` and produces a `⏱` line; `finalize()` already computes `hook_timing_stats` (count, avg_ms, p95_ms, max_ms). There is just no producer.

Facility 2 — `HookTimer` class

File: `packages/claude-code-plugin/hooks/lib/hook_timer.py`

A complete `HookTimer` class with `start()`, `stop()`, `get_stats()`, `get_warnings()` exists. It is also never imported by any hook:

```bash
cd packages/claude-code-plugin
rg -n 'HookTimer|hook_timer' hooks/

Only match: hooks/lib/hook_timer.py — the definition itself.

```

Why this matters

• The whole purpose of feat: Adaptive hook timeout — track execution time and suggest adjustments #945 (per the docstrings) was "adaptive hook timeout tracking" + "warnings for hooks approaching their timeout threshold". Today neither happens because no hook actually times itself.
• The `format_summary()` Stop hook output is missing a feature users would benefit from: knowing whether their hooks are getting slow.
• The presence of two parallel facilities (`SessionStats.record_hook_timing` and `HookTimer`) is confusing — one of them should be deleted, the other wired up.

Recommended approach

Step 1 — Decide which facility to keep

Facility	Strengths	Weaknesses
`SessionStats.record_hook_timing`	Persists across processes (disk-backed); already consumed by `format_summary`/`finalize`	Adds disk I/O to every hook
`HookTimer`	In-memory only, no I/O cost	Per-process only, dies with the process — useless for short-lived hooks

Recommendation: keep `SessionStats.record_hook_timing` (cross-process is the only model that makes sense for short-lived hook processes), delete `hook_timer.py` and its tests. `HookTimer` cannot work for the actual deployment topology.

Step 2 — Wire it up

For each hook script in `packages/claude-code-plugin/hooks/` (`pre-tool-use.py`, `post-tool-use.py`, `session-start.py`, `stop.py`, `user-prompt-submit.py`):

1. Capture `time.monotonic()` at the very top of the handler.
2. In a `finally:` block (so it runs even on early exit), compute `elapsed_ms = (time.monotonic() - start) * 1000`.
3. Call `SessionStats(session_id=...).record_hook_timing(hook_name, elapsed_ms)` followed by `stats.flush()` (same short-lived-process pattern as fix(hooks): persist tool stats from short-lived hook processes #1492).

Hook name should match the Claude Code hook event name exactly: `PreToolUse`, `PostToolUse`, `SessionStart`, `Stop`, `UserPromptSubmit`.

Step 3 — Verify the Stop summary now includes timings

After this change, a session that calls a few tools should produce a Stop hook summary like:

```
[CB] 3m | 12 tools | 0 errors | Bash:5 Edit:3 Read:4 | ⏱ PostToolUse:42ms PreToolUse:8ms Stop:120ms
```

The `⏱` segment is what proves the producer is now wired.

Acceptance criteria

• `packages/claude-code-plugin/hooks/lib/hook_timer.py` and its tests deleted (or alternatively, decide and document why `HookTimer` should stay alongside `record_hook_timing`).
• Each hook script in `packages/claude-code-plugin/hooks/*.py` measures its own elapsed time and calls `SessionStats.record_hook_timing(hook_name, elapsed_ms)` followed by `flush()` in a `finally` block.
• Hook timing recording must NOT raise — exceptions in this path swallowed (matching the existing `# Never block tool execution` pattern in those hooks).
• New regression test in `packages/claude-code-plugin/tests/` that:
  • Imports the post-tool-use handler module
  • Invokes its handler with a fake event
  • Asserts the on-disk `hook_timings["PostToolUse"]` list has at least one entry
• Manual verification: in a real Claude Code session, the Stop summary contains the `⏱` segment with at least one hook name and a non-zero ms value.
• Existing `TestHookTimingIntegration` tests in `tests/test_stats.py` still pass.

Reproduction (current dead-code state)

```bash
cd packages/claude-code-plugin

Verify record_hook_timing is dead:

rg -n 'record_hook_timing' hooks/ # only the definition

Verify HookTimer is dead:

rg -n 'HookTimer|hook_timer' hooks/ # only the definition

Verify the Stop summary never emits the ⏱ segment in practice:

cat ~/.codingbuddy/*.json 2>/dev/null | python3 -c "import json, sys; [print(k, v) for k, v in json.loads(sys.stdin.read()).items() if 'timing' in k]"

Expected output today: hook_timings {} — empty.

```

References

• Discovered while reviewing fix(hooks): persist tool stats from short-lived hook processes #1492 (`fix(hooks): persist tool stats from short-lived hook processes`).
• Related: race condition issue for `SessionStats.flush()` (separate issue, also discovered during fix(hooks): persist tool stats from short-lived hook processes #1492 review).
• Touched files (read-only context):
  • `packages/claude-code-plugin/hooks/lib/stats.py` — `record_hook_timing`, `format_summary`, `finalize`
  • `packages/claude-code-plugin/hooks/lib/hook_timer.py` — entire file (candidate for deletion)
  • `packages/claude-code-plugin/hooks/post-tool-use.py` — example caller that needs the `finally`-block wiring
  • `packages/claude-code-plugin/tests/test_stats.py` — `TestHookTimingIntegration` already covers the consumer side