fix: harden closed-subagent tombstones and kimi hooks status

[zephyr110]

Summary

Follow-ups for the LOW notes on #262 and #274:

• Closed-subagent ids (fix(sessions): fold Cursor Tasks under Agent Sub-Sessions like Codex #262 b): closedSubagentIds is an ordered list (newest last) with a live keep-last-256 cap, O(1) hasClosedSubagentId, and mutate-only APIs. Persist keeps insertion order (no .sorted()). Restore loads all disk ids (no fake-recency trim); the live cap applies on new record only. Permission/Question suppress uses hasClosedSubagentId.
• AppState teardown (fix(sessions): fold Cursor Tasks under Agent Sub-Sessions like Codex #262 a): Timers + FSEvents tear down in one main-queue hop from deinit; stopSessionDiscovery also invalidates rotationTimer.
• Cursor probe (fix(sessions): fold Cursor Tasks under Agent Sub-Sessions like Codex #262 c): Require agent-transcripts plus _source of cursor / cursor-cli (compact literals → whitespace-tolerant regex → JSON only if \u is present). Drop write-only _cursor_subagent_session_id / _cursor_subagent_event.
• Kimi hooks status (fix: detect Kimi Code CLI under ~/.kimi-code #274 c): Installed badge checks only cli.fullPath (install target). Uninstall still scrubs modern + legacy.
• Kimi wire (fix: detect Kimi Code CLI under ~/.kimi-code #274 b): Prefer turn.prompt over a preceding context.append_message; empty turn.prompt does not wipe append text; consecutive prompts do not drop the prior user line.
• Kimi discovery (fix: detect Kimi Code CLI under ~/.kimi-code #274 a): Unit coverage for discoverKimiCodeSessionFromIndex via a test seam (private type unchanged).

中文说明

针对 #262 与 #274 的 LOW 跟进：

• Closed-subagent ids（fix(sessions): fold Cursor Tasks under Agent Sub-Sessions like Codex #262 b）： closedSubagentIds 改为有序数组（最新在末尾），运行时 keep-last-256，O(1) hasClosedSubagentId，仅经 mutate API 写入。持久化保留插入序（不再 .sorted()）。restore 保留磁盘全部 id（不做假 recency 截断）；cap 只在新的 record 时生效。Permission/Question 抑制改走 hasClosedSubagentId。
• AppState teardown（fix(sessions): fold Cursor Tasks under Agent Sub-Sessions like Codex #262 a）： deinit 在一次主线程 hop 内拆掉 Timer + FSEvents；stopSessionDiscovery 也会 invalidate rotationTimer。
• Cursor 探针（fix(sessions): fold Cursor Tasks under Agent Sub-Sessions like Codex #262 c）： 需要 agent-transcripts 且 _source 为 cursor / cursor-cli（compact 字面量 → 冒号两侧空白的 regex → 仅当存在 \u 时才 JSON）。删除只写字段 _cursor_subagent_session_id / _cursor_subagent_event。
• Kimi hooks 状态（fix: detect Kimi Code CLI under ~/.kimi-code #274 c）：「已安装」只检查 cli.fullPath（安装目标）。卸载仍同时清理 modern + legacy。
• Kimi wire（fix: detect Kimi Code CLI under ~/.kimi-code #274 b）： 若先有 context.append_message，后续 turn.prompt 优先替换用户文本；空的 turn.prompt 不擦掉 append 内容；连续 turn.prompt 不会丢掉上一轮用户行。
• Kimi discovery（fix: detect Kimi Code CLI under ~/.kimi-code #274 a）： 为 discoverKimiCodeSessionFromIndex 增加单测（经 test seam；DiscoveredSession 仍保持 private）。

Test Plan

• ClosedSubagentIdsCapTests
• HookServerCursorProbeTests (compact / spaced / \u / negatives)
• ConfigInstallerTests (status path lock + migration false-positive)
• KimiCodeSessionDiscoveryTests
• KimiTranscriptTests (both orders, consecutive prompts, empty prompt)
• Related: CursorSessionFoldingTests, AppStateCursorSubsessionTests