feat(tasks): the hand-off — SessionEnd releases a session's claims; the practice is written down (milestone 381 step 4)

Release is the mechanical half: scribe_session_end.sh sends the ending
session's id to /api/plugin/release-session, which releases the claims it
held. A tidy-up, not the guarantee (no SessionEnd on a crash; the lease
covers that), and skipped on /clear so SessionStart(clear) can still
hand the claimed work back.

Saying what happened is the half only the model can do. It is stated as a
practice where it is read: the using-scribe skill owns it ("Hand off before
this session's context stops existing", pinned in test_guidance_ownership),
the static context points at it for the wrap-up moment, and add_task_log's
docstring says a log claims the task. _INSTRUCTIONS is untouched.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

plugin/.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "scribe",
   "description": "Scribe for Claude Code: connects the scribe MCP server, adds the hooks that deliver live project state and relevant records at the right moment, ships the shared client-neutral Scribe skills (using-scribe, writing-plans, reporting-back, systematic-debugging, verification, brainstorming, reusing-code, shape-accounting), and syncs your saved Scribe Processes as skills (/scribe:sync).",
-  "version": "2026.09.24.1041",
+  "version": "2026.09.24.1042",
   "author": {
     "name": "Bryan Van Deusen"
   },