fix(team-mode): make lead close teams on its own initiative

The lead currently leaves teams alive after the task list drains because
none of the prompt surfaces tell it WHEN to close or HOW. omx-style
'self-closing' behavior was missing for four reasons (diagnosed via
prompt-engineering A/B/C: wrong / misframed / missing):

1. builtin team-mode skill 'Lifecycle' (B+C): 'phase ends / shape
   outgrown' is qualitative, so the model maps it to 'wait for user'.
   Step 6 jumped to team_delete without the request/approve pair the
   tool contract requires. Replaced with a 'Closure Contract' (a
   computable predicate over team_task_list + team_status) and an
   explicit 'Closure Sequence' (request -> approve -> delete, with
   force=true reserved for unrecoverable paths only).

2. TEAM_MESSAGE keyword injection (C): spent 100%% of its one-shot
   budget on routing ('do not substitute delegate_task'), 0%% on
   closure. Added the same closure rule in compressed form. Kept the
   'NEVER substitute with delegate_task' literal that
   keyword-detector/index.test.ts depends on.

3. team-mode-status-injector body (C): the only per-session injection
   for team mode had no closure obligation. Replaced the optional
   'load the team-mode skill ... otherwise use the team_* tools'
   sentence with a 'Closure invariant' clause that ties the check to
   every team_task_update.

4. member-guidance Wrap-up (A+B): step 3 said 'so the lead can decide
   whether to request shutdown', but team_shutdown_request is
   lead-only - members cannot initiate it. Step ordering also placed
   the completion message before team_task_update, so the lead's
   closable check would see stale data. Reordered to
   task_update -> check task_list for new work -> if nothing left,
   send a single 'closure-ready' message and idle. Test assertion
   updated to match the new accurate contract.

Also: stripped Korean alternation from TEAM_PATTERN per directive
('절대로 코드 내에 한국어 적지 마라'). Pattern is now
/\\bteam[\\s_-]?mode\\b/i. Removed 4 Korean test cases
(2 positive triggers + 2 false-positive guards) that the pattern no
longer needs to defend, and updated the keyword-detector AGENTS.md
row.

Net: -71 lines across prompt surfaces. The Closure Contract is the
only addition; everything else tightened.

Tests: 428/428 pass across src/features/team-mode/,
src/features/builtin-skills/, src/hooks/keyword-detector/,
src/hooks/team-mode-status-injector/, src/hooks/team-mailbox-injector/,
src/hooks/team-tool-gating/, src/hooks/team-session-events/.
LSP: no errors introduced (one pre-existing error in
keyword-detector/index.test.ts confirmed pre-existing on dev).

src/hooks/keyword-detector/team/default.ts

@@ -2,16 +2,10 @@
  * Team mode keyword detector.
  *
  * Triggers when the user explicitly invokes team-mode work:
- * - English: team mode, team-mode, team_mode, teammode (case-insensitive)
- * - Korean: 팀 모드, 팀모드, 팀으로
- *
- * The Korean variants use a negative lookbehind on Hangul syllables (가-힣)
- * to prevent false positives like "스팀으로" matching "팀으로", or
- * "스팀모드" matching "팀모드".
+ *   team mode, team-mode, team_mode, teammode (case-insensitive)
  */
 
-export const TEAM_PATTERN =
-  /\bteam[\s_-]?mode\b|(?<![가-힣])(?:팀\s*모드|팀으로)/i
+export const TEAM_PATTERN = /\bteam[\s_-]?mode\b/i
 
 export const TEAM_MESSAGE = `[team-mode]
-Team mode reference detected. If user wants team-mode work, MUST orchestrate via team_* tools (team_create -> team_task_create + team_send_message). NEVER substitute with delegate_task - it is not equivalent. If team_* tools are unavailable (team_mode disabled in config), instruct user to set team_mode.enabled=true and restart opencode.`
+Team-mode reference detected. Orchestrate via team_* tools (team_create -> team_task_create + team_send_message); NEVER substitute with delegate_task — it is not equivalent. After every team_task_update that completes or fails a task, re-check team_task_list: if every task is terminal, run the closure sequence (team_shutdown_request + team_approve_shutdown per active member, then team_delete) in the same turn. Closing the team is the lead's responsibility, not the user's. If the team_* tools are absent, team_mode is disabled — tell the user to set team_mode.enabled=true and restart opencode.`