docs: remove deleted project docs skill requirement

.project-docs/05-agent-entry/concurrent-task-gate.md

@@ -1,30 +1,41 @@
-# Concurrent Task Gate
+# Concurrent Worktree Check
 
-Complete this gate before the Planning Gate.
+Complete this repository-local check before the Planning Gate. It does not require an external Skill, `task_context.py`, or a separate ownership registry.
+
+## Commands
+
+Run from the intended repository worktree:
+
+```bash
+git status --short
+git branch --show-current
+git rev-parse --show-toplevel
+git worktree list --porcelain
+git rev-parse HEAD
+```
 
 ## Invariants
 
-- One active task owns one worktree.
+- One worktree carries edits for only one active task at a time.
 - Concurrent tasks use different branches and worktrees.
 - Never stash, reset, move, delete, or adopt unknown work automatically.
 - Feature tasks write only their own task record and uniquely named supporting records.
-- Keep the active task record present until ownership is released.
-- Treat `start`, `touch`, `complete`, and `release` as serialized registry transactions; lock timeout or malformed registry state blocks the gate.
+- Keep an active task record for repository-changing work.
+- Treat task records as collaboration context, not locks. Git worktree identity and visible status are the authoritative local safety inputs.
 - Feature-task write boundaries in this gate supersede legacy instructions to update shared or canonical project documents.
 
 ## Required Output
 
-- Task ID:
-- Mode: Feature | Integration
 - Branch:
 - Worktree:
 - Base commit:
-- Ownership result: Claimed | Resumed | Isolated | Blocked
-- Other active local tasks:
+- Existing changes in this worktree:
+- Other local worktrees relevant to this scope:
+- Overlap result: Clear | Isolated | Blocked
 
 ## Block Conditions
 
-- The worktree belongs to another active task and isolation did not succeed.
-- An unowned worktree contains staged, unstaged, or untracked changes.
+- Existing changes overlap the intended edit and cannot be safely preserved or attributed.
+- The intended branch or worktree is ambiguous, or isolation from a conflicting task did not succeed.
 - No reliable committed base was selected for a new worktree.
 - The runtime cannot keep later Git and file operations rooted in the isolated worktree.