Add the task-startup gate scripts and local hooks

Why: agents skipped triggered reading and wrote into shared checkouts holding
other tasks' in-flight changes; the 2026-09-30 empty-list incident session
found 24 overlapping in-flight files only by accident at first write.
Evidence: positive/negative suite in a real scratch repo passed 19/19
(precheck READY/BUSY/SYNC_REQUIRED, start refuse/establish, hook main/badname/
longsubject refusals, sync checkpoint, finish recycle and abandon double-
confirm); the suite caught three real defects (pipefail empty-grep abort,
worktree gitdir COMMIT_EDITMSG resolution, message checks in the wrong hook
phase).
Impact: make setup enables pre-commit/commit-msg hooks; make precheck/task-
start/task-sync/task-finish provide the governed path; no existing workflow
removed. AGENTS.md carries the resident gate rules.
Refs: Development-Guidelines 0.1.0-draft.7; task card .task/delivery-mechanism.md

scripts/hooks/pre-commit

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+# 本地硬闸（pre-commit）：集成分支直提拒绝 + 分支命名。权威准入在 PR（baseline.md:26）。
+branch=$(git rev-parse --abbrev-ref HEAD)
+case "$branch" in
+  main|master)
+    echo "pre-commit: 拒绝——集成分支 ${branch} 不得直接提交，走 feature 分支 + PR（collaboration.md）" >&2
+    exit 1 ;;
+esac
+echo "$branch" | grep -qE '^(feature|fix|hotfix|release)/[A-Za-z0-9._-]+$' || {
+  echo "pre-commit: 拒绝——分支名须为 feature|fix|hotfix|release/<slug>，当前：${branch}" >&2
+  exit 1
+}
+exit 0