feat(hooks): add duration_ms to post_tool_call + transform_tool_result

Plugin hooks fired after a tool dispatch now receive an integer
duration_ms kwarg measuring how long the tool's registry.dispatch()
call took (time.monotonic() before/after). Inspired by Claude Code
2.1.119 which added the same field to PostToolUse hook inputs.

Wire points:
- model_tools.py: measure dispatch latency, pass duration_ms to
  invoke_hook("post_tool_call", ...) and invoke_hook("transform_tool_result", ...)
- hermes_cli/hooks.py: include duration_ms in the synthetic payload
  used by 'hermes hooks test' and 'hermes hooks doctor' so shell-hook
  authors see the same shape at development time as runtime
- shell hooks (agent/shell_hooks.py): no code change needed;
  _serialize_payload already surfaces non-top-level kwargs under
  payload['extra'], so duration_ms lands at extra.duration_ms for
  shell-hook scripts

Plugin authors can now build latency dashboards, per-tool SLO alerts,
and regression canaries without having to wrap every tool manually.

Test: tests/test_model_tools.py::test_post_tool_call_receives_non_negative_integer_duration_ms
E2E: real PluginManager + dispatch monkey-patched with a 50ms sleep,
hook callback observes duration_ms=50 (int).

Refs: https://code.claude.com/docs/en/changelog (2.1.119, Apr 23 2026)

website/docs/guides/build-a-hermes-plugin.md

@@ -414,7 +414,7 @@ Each hook is documented in full on the **[Event Hooks reference](/docs/user-guid
 | Hook | Fires when | Callback signature | Returns |
 |------|-----------|-------------------|---------|
 | [`pre_tool_call`](/docs/user-guide/features/hooks#pre_tool_call) | Before any tool executes | `tool_name: str, args: dict, task_id: str` | ignored |
-| [`post_tool_call`](/docs/user-guide/features/hooks#post_tool_call) | After any tool returns | `tool_name: str, args: dict, result: str, task_id: str` | ignored |
+| [`post_tool_call`](/docs/user-guide/features/hooks#post_tool_call) | After any tool returns | `tool_name: str, args: dict, result: str, task_id: str, duration_ms: int` | ignored |
 | [`pre_llm_call`](/docs/user-guide/features/hooks#pre_llm_call) | Once per turn, before the tool-calling loop | `session_id: str, user_message: str, conversation_history: list, is_first_turn: bool, model: str, platform: str` | [context injection](#pre_llm_call-context-injection) |
 | [`post_llm_call`](/docs/user-guide/features/hooks#post_llm_call) | Once per turn, after the tool-calling loop (successful turns only) | `session_id: str, user_message: str, assistant_response: str, conversation_history: list, model: str, platform: str` | ignored |
 | [`on_session_start`](/docs/user-guide/features/hooks#on_session_start) | New session created (first turn only) | `session_id: str, model: str, platform: str` | ignored |