Pin T1 contracts combo and guard task-finish against wrong cwd

Why: Provider repos merged for T1 (core PR#2, agent-command PR#2, frontend
  PR#3, ui PR#3, documents PR#9); gitlinks pinned to those mains. The
  task-finish guard prevents a repeat of the T0 incident where running
  finish from the main checkout deleted it (scripts/task.sh treated $PWD as
  the worktree to remove).

Evidence: make test green on the pinned combo — core, backend 13 pkgs,
  frontend 9, ui 6, agent-command (vet + tests incl. conformance); make build
  produces the binary; combo version string now includes agentcmd SHA.

Impact: combo grows its version traceability; AGENTS.md documents the
  worktree-cwd requirement for finish.

Refs: modules/documents docs/records/2026-09-30-t1-core-cards-commands-verification.md

AGENTS.md

@@ -11,8 +11,9 @@
   feature 分支（自动记录 R0 与任务卡）；任务中途不重复运行 precheck。
 - **验收、请求审核、合入前**各运行一次 `make task-sync`；完成声明附 precheck、task-sync、
   测试三段输出。
-- 合入后运行 `make task-finish` 回收 worktree 与分支；放弃未合入工作用
-  `make task-finish ABANDON="--abandon <原因>"` 并记录原因。
+- 合入后**在 worktree 内**运行 `make task-finish` 回收 worktree 与分支（脚本会把
+  当前目录当 worktree 回收——在主检出运行会误删主检出，已加防护）；放弃未合入
+  工作用 `make task-finish ABANDON="--abandon <原因>"` 并记录原因。
 
 ## 提交与 PR