Stop task-finish from uninitializing shared submodule config

Why: cmd_finish ran git submodule deinit --all, but submodule.<name>.url entries live in the shared .git/config — finishing any task silently marked every other checkout and worktree uninitialized (observed twice on 2026-09-30: main checkout uninit=12 after each finish; a parallel session hit it minutes before this fix landed). The deinit serves no purpose: worktree removal with gitlinks is refused regardless, so cleanup already goes through rm -rf + prune. Also aligns AGENTS.md with observed hook behavior (post-merge fires on ff-only pulls too, and its inline close cannot see cards merged remotely until they are pulled), and ignores the ZCode-generated .zcodeignore that tripped the BUSY gate in every session.
Evidence: bash -n clean; abandon-path smoke of the patched script — start + FORCE_ABANDON=1 finish of a throwaway branch left shared submodule url config at 12 entries (pre-fix: 0), main checkout submodule status uninit=0, smoke worktree and branch fully recycled; the smoke close also backfilled a parallel session card left open (gitea-access-facts) via a card-close branch, proving the fallback path.
Impact: scripts/task.sh cmd_finish only (removes one line, updates comment), AGENTS.md card-close paragraph, .gitignore one entry. No product or gitlink change; make test not applicable (repo-level tooling/docs only). web_base default fix intentionally withdrawn from this PR — landed via parallel PR #73.
Refs: .task/fix-task-finish-close-followups.md

scripts/task.sh

@@ -267,9 +267,9 @@ cmd_finish() {
     git merge-base --is-ancestor "$head" "origin/${TARGET_BRANCH}" || die "分支未合入 origin/${TARGET_BRANCH}——先走 PR 合入；放弃则用 --abandon <reason>"
     echo "[verified] ${branch} 已包含于 origin/${TARGET_BRANCH}；成果已落盘"
   fi
-  git submodule deinit --all -f >/dev/null 2>&1 || true
-  # git 对含 gitlink 的 worktree 无条件拒绝 remove（查索引，与 deinit 无关）：
-  # 已验证合入且子模块已 deinit 后，直接清目录并 prune。
+  # git 对含 gitlink 的 worktree 无条件拒绝 remove（查索引），回收走 rm -rf + prune。
+  # 此处不得跑 submodule deinit：submodule.<name>.url 写在共享的 .git/config 里，deinit
+  # 会把其他检出/worktree 的子模块一并标成未初始化（2026-09-30 实测 finish 后主检出 uninit=12）。
   git -C "$mainrepo" worktree remove "$PWD" 2>/dev/null || { rm -rf "$PWD"; git -C "$mainrepo" worktree prune; }
   git -C "$mainrepo" branch -d "$branch" 2>/dev/null || git -C "$mainrepo" branch -D "$branch"
   git -C "$mainrepo" worktree prune