feat(狀態回報): 收尾寫一筆 skill-end 事件

現行紀錄只記「被叫用」，沒有成敗也沒有結束碼。跑完整輪的技能與開場就
中止的技能，在紀錄裡長得一模一樣。

start 由技能用量 hook 順手發，不必改技能文件。end 只能由技能自己在收尾
步驟寫——hook 接在技能工具呼叫上，而實際工作發生在之後的模型輪次，它在
原理上看不到成敗。有 start 沒有配對的 end，就是那一輪中止了。

status 五選一，每支技能各自寫明什麼情況選哪一個。找不到回報腳本就安靜
跳過，回報失敗一律不改變技能自己的結論。

skills/skill-update/SKILL.md

@@ -53,3 +53,24 @@ Single source of guidelines: [`../../references/guidelines.md`](../../references
         | | 8 | Some other API failure. Stop, report that status, and create no page |
 
       On any failure, hand the page name and the unwritten entry back to the user and leave this step open; never close the flow on an unwritten report. Completion condition: `SKILLSET_{HASH}` holds the new section plus all earlier sections, and `wiki-contents.sh upsert` exited 0 with this domain's row on `SKILLSET_CONTENTS` linking that page by absolute URL.
+9. Report this run's outcome to the local event stream — the last step of every run, the ones that stop early included. Run:
+
+   `jsc-hooks/tools/report-status.sh skill-end jsc-meta:skill-update {status} {exit code} [detail]`
+
+   Resolve `jsc-hooks` from the `domain<TAB>path` row step 1 printed for the `hooks` domain, the same way this skill resolves every other cross-plugin script. **When that script is not on this machine, skip this step in silence and close the run as normal.** A reporting path that is absent must never fail the run it reports on, and this call's own exit code never changes what this skill reports.
+
+   Pick `{status}` from what the run actually did:
+
+   | status | Use it when |
+   | --- | --- |
+   | `ok` | the skill files and the behavior-list section carry the change, the checklist passes, the PR is open, `deploy-verify.md` sections 1 to 5 hold, and both wiki writes exited 0 |
+   | `blocked` | a gate or a missing prerequisite stopped the run before any file changed — `sync-domains.sh` never reached exit 0, or no skill could be listed to pick from |
+   | `failed` | the run broke mid-way — the step 6 checklist loop kept failing, or a wiki write failed again after its one retry |
+   | `degraded` | the update landed with a part missing — the content page was written while its `SKILLSET_CONTENTS` row was not, or a CLI could not be verified and the reason was recorded |
+   | `aborted` | the user stopped the run, or a prerequisite turned out not to hold and this skill stopped on its own |
+
+   `{exit code}` is this run's own result as a number: `0` for `ok`, non-zero otherwise. `detail` is optional, one line, at most 200 characters.
+
+   The matching `skill-start` comes free from the hook, which fires when the skill loads. The update itself happens in the model turns after that, so no hook can see how the run ended — a `start` with no `end` reads as an abort, which is why writing the `end` is this skill's own job.
+
+   Completion condition: one `skill-end` line for this run is appended to `$JSC_HOME/usage/events.jsonl`, or the script was absent and the final report says so.