fix(mcp): honor the create-issue bootstrap in anti-stomp preflight (Closes #757)

The sanctioned create_issue bootstrap from #749/#750 was unreachable in
production. Two guards assessed the same workspace for the same task and
reached opposite conclusions: the #274 branches-only guard consulted the
bootstrap and permitted a clean canonical control checkout, then the #604
anti-stomp preflight -- which never consulted it -- rejected that same
checkout as wrong_worktree.

The defect was wiring, not policy: the bootstrap decision was computed in
one guard and discarded, while the other re-derived a conflicting answer
from a lower-level assessor with no notion of the bootstrap phase.

Fix: one computation site, one interpretation site.

* create_issue_bootstrap.bootstrap_permits_control_checkout() is the single
  predicate both guards use to interpret an assessment. It is fail-closed by
  construction: missing, malformed, refused, incomplete, or contradictory
  evidence returns False and leaves the ordinary block in force. It also
  verifies the assessment describes the exact workspace and canonical root
  being guarded, so a stale or foreign assessment cannot be reused.
* _create_issue_bootstrap_assessment() computes the assessment once per
  preflight from inspected repository state. verify_preflight_purity threads
  that single result into both guards.
* The #604 assessor accepts the assessment and waives ONLY the wrong-worktree
  verdict. Root checkout, repo, role, stale runtime, lease, head-SHA,
  workflow-hash, and contamination checks are evaluated independently and
  still apply.

Evidence is server-derived only and travels an internal path: no MCP tool
signature gains a bootstrap argument, and no caller-controlled boolean can
manufacture eligibility. Behavior is unchanged for callers that supply no
evidence, and for every non-create_issue author mutation.

No issue or PR number is special-cased in production behavior.

Tests: new tests/test_issue_757_bootstrap_guard_agreement.py (38 tests, 26
subtests) covering the shared predicate, the narrow waiver, guard agreement
across the full workspace-state matrix, non-forgeable eligibility, and an
end-to-end native gitea_create_issue run with the #604 gate LIVE. All 38
fail against unfixed sources; the e2e reproduces the production error text
verbatim ("Anti-stomp preflight (#604) blocked mutation [wrong_worktree]").

tests/test_reconciler_close_workspace_guard.py: one case asserted that
create_issue stays blocked on the control checkout, which only held because
the bootstrap-blind #604 guard was overriding #750 -- it encoded the defect.
Re-pointed to lock_issue, which is issue-backed and legitimately still
requires a branches/ worktree. Its teardown now restores the module-level
preflight task/role so test order cannot leak resolved state.

Full suite: 3624 passed, 2 failed, 6 skipped (426 subtests).
Baseline at bde5c5fb on a clean detached worktree: 3586 passed, 2 failed,
6 skipped (400 subtests). The same 2 failures reproduce identically on
pristine master and are unrelated to this change
(test_issue_702_review_findings_f1_f6 F1 worktree recovery;
test_reconciler_supersession_close org/repo forwarding).

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

anti_stomp_preflight.py

@@ -33,6 +33,7 @@ from __future__ import annotations
 from typing import Any
 
 import author_mutation_worktree
+import create_issue_bootstrap
 import master_parity_gate
 import remote_repo_guard
 import root_checkout_guard
@@ -354,6 +355,7 @@ def assess_anti_stomp_preflight(
     remote_master_sha: str | None = None,
     check_root_checkout: bool = True,
     check_worktree: bool = True,
+    create_issue_bootstrap_assessment: dict[str, Any] | None = None,
     # stale runtime (master parity)
     startup_head: str | None = None,
     current_code_head: str | None = None,
@@ -584,12 +586,28 @@ def assess_anti_stomp_preflight(
             project_root=project_root,
             current_branch=current_branch,
         )
+        # #757: the #274 guard consults the server-derived create_issue
+        # bootstrap before blocking the canonical control checkout. Route this
+        # guard's decision through the *same* predicate on the *same*
+        # assessment so the two cannot disagree about identical evidence.
+        # Only the wrong-worktree verdict is waived; every other check in this
+        # assessment (root checkout, repo, role, stale runtime, lease, ...) is
+        # evaluated independently and still applies.
+        bootstrap_waived = wt.get("block") and (
+            create_issue_bootstrap.bootstrap_permits_control_checkout(
+                create_issue_bootstrap_assessment,
+                task=task_name,
+                workspace_path=workspace_path,
+                canonical_repo_root=project_root,
+            )
+        )
         checks["worktree"] = {
-            "block": bool(wt.get("block")),
+            "block": bool(wt.get("block")) and not bootstrap_waived,
             "reasons": list(wt.get("reasons") or []),
             "under_branches": wt.get("under_branches"),
+            "create_issue_bootstrap_waived": bool(bootstrap_waived),
         }
-        if wt.get("block"):
+        if wt.get("block") and not bootstrap_waived:
             blockers.append(
                 _blocker(
                     BLOCKER_WRONG_WORKTREE,