fix(agent-core-v2): fire external Stop hooks on completed turns - #4902

…2296)

## Summary

Until now, no Esc-cancelled kimi turn reached the office as a turn end. On a cancel, kimi fires `Interrupt` instead of `Stop`, and `KIMI_EVENTS` never installed `Interrupt`.

- **What a cancel does in kimi:** it ends the turn as `cancelled`. That fires `Interrupt` with `{ turn_id, reason: "cancelled" }` (`packages/agent-core-v2/src/features/externalHooks/agent/agentExternalHooksService.ts:422-424` at `@moonshot-ai/kimi-code@2.5.3`). The aborted step skips the after-step hooks that fire `Stop` (`agent/loop/loopService.ts:1922-1938`, same ref). The docs say the same: "fires in place of `Stop`" (`docs/en/customization/hooks.md:130`).
- **What the user saw:** an Esc while a tool runs leaves the sprite Running on that call until the stale sweep.
  - Each tool runs on its own scope's signal (`human/agent/machine.ts:415-421`), and `PostToolUse` fires with the call's signal (`agentExternalHooksService.ts:358`).
  - Leaving the turn aborts every tool scope in it (`human/agent/machine.ts:750-755` → `:446-457`).
  - `runHook` kills a hook whose signal has already aborted (`features/externalHooks/internal/runHook.ts:120-128`).
  - So that tool's `PostToolUse` never lands. `Interrupt` carries no signal, so it survives the abort: its call passes none (`agentExternalHooksService.ts:423`) to `fireAndForget`'s optional `signal` (`:126`), same ref.
- **Decoding:** `Interrupt` is now in `KIMI_EVENTS`, and `decode_kimi_hook_custom` decodes it the way it decodes `Stop` and `StopFailure`. It emits the session's `Identity`, since it is a per-turn hook like those two, then the shared `Stop` arm's `TurnEnd`.
- **Existing installs:** a kimi install connected before this change has no `Interrupt` entry. Until kimi is reconnected in the Sources panel, it reports `missing hook entries for: Interrupt … reconnect via the Sources panel` at launch and in `doctor` (`install/verify.rs:136-141`), and Esc-cancelled turns still don't end. Launch never merges config on its own: a config merge needs the consent that only `connect` asks for (`install/mod.rs:326-328`). That existing warning already names the reconnect, so this PR adds no `NOTICES` entry.
- **One rule across CLIs:** an interrupted turn end is the same `TurnEnd` a completed one is. codex's `turn_aborted` already shares `EM_TURN_END` with `task_complete` (`source/codex.rs:287`). opencode's `session.execution.interrupted` shares the succeeded/failed arm (`source/opencode.rs:177-181`).
- **New recorded scenario:** kimi's TUI profile now cancels with Esc. In 2.5.3, Esc cancels a streaming turn (`apps/kimi-code/src/tui/controllers/editor-keyboard.ts:259-262`). A `cancel` scenario, recorded at the 2.5.3 pin, pins the wire.
  - The recorded `Interrupt` payload is `hook_event_name`, `session_id`, `cwd`, `client_type`, `session_title`, `turn_id`, `reason`. The strip blanked the last four, which no decoder reads.
  - `screens/cancel.txt` is the run's own `tui_drive` dump of the screen it cancelled at: `HERMETIC-STREAM` painted mid-stream.

## Related issue

None. This does NOT close #2285 (kimi 2.6.x never fires `Stop`). That issue stays open until a kimi release carries upstream MoonshotAI/kimi-code#4902. `Interrupt` is not affected by that regression: it rides the `TurnEnded` subscription (`agentExternalHooksService.ts:247`, `:414-422` at `@moonshot-ai/kimi-code@2.6.1`), not the guarded `onDidFinishStep` path. Tracked on the Roadmap as the draft "kimi: an Esc-cancelled turn ends (Interrupt hook)".

## Type of change

- [x] Bug fix

## How I tested it

- **TDD:** adding `Interrupt` to `KIMI_EVENTS` and its roster pin (`kimi_events_pins_the_exact_registered_set`) turned `every_registered_kimi_event_decodes` red (unsupported event). Adding `Interrupt` rows to the core decoder tests' own tables turned `a_failure_or_cancel_decodes_as_its_shared_arm` and `a_claimed_event_without_session_id_errs_and_breadcrumbs` red. Those two read their own tables, not `KIMI_EVENTS`. The decoder arm turned all three green.
- **Byte proof:** `sources::kimi::a_turn_end_alone_registers_its_session` gains a `("cancel-hermetic", "Interrupt")` row. The recorded `Interrupt` alone registers its session.
- **Replay hermetically (REVIEW.md must-run, hook integration):** ran `just hermetic --record kimi` at the pin (kimi 2.5.3, aimock 1.47.0, macOS, unbilled):
  ```
  == kimi/tool-run      Pass
  == kimi/permission    Pass
  == kimi/cancel        Pass
  == kimi/model-error   Pass
  == kimi (every scenario)  Pass
  kept kimi/tool-run: the run renamed only its ids
  kept kimi/permission: the run renamed only its ids
  recorded kimi/cancel into .../tests/sources/kimi/fixtures/cancel-hermetic
  kept kimi/model-error: the run renamed only its ids
  ```
- **Suites:** `just test -p pixtuoid-core` passed 1841/1841 and `just test -p pixtuoid --lib` passed 1608/1608. The pre-push preflight passed.

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