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]>

gitea_mcp_server.py

@@ -817,10 +817,56 @@ def _enforce_canonical_repository_root(
         )
 
 
+# #757: distinguishes "caller supplied no bootstrap evidence" (compute it) from
+# "caller supplied a not-applicable/refused assessment" (honour it, fail closed).
+_BOOTSTRAP_UNSET = object()
+
+
+def _create_issue_bootstrap_assessment(
+    task: str | None,
+    worktree_path: str | None = None,
+) -> dict | None:
+    """#757: the single server-derived create_issue bootstrap assessment.
+
+    Computed once per preflight from inspected repository state, then consumed
+    by BOTH the #274 branches-only guard and the #604 anti-stomp preflight so
+    the two cannot reach opposite conclusions about identical evidence.
+
+    Returns ``None`` when *task* is not a create_issue mutation, which leaves
+    every other author mutation on the ordinary branches-only path. The result
+    is derived from inspected repository state only — never from an MCP tool
+    argument.
+    """
+    import create_issue_bootstrap as _cib
+
+    if not _cib.is_create_issue_task(task):
+        return None
+
+    ctx = _resolve_namespace_mutation_context(worktree_path)
+    workspace = ctx["workspace_path"]
+    git_state = issue_lock_worktree.read_worktree_git_state(workspace)
+    try:
+        remote_master_sha = root_checkout_guard.resolve_remote_master_sha(
+            ctx["canonical_repo_root"]
+        )
+    except Exception:
+        remote_master_sha = None
+    return _cib.assess_create_issue_bootstrap(
+        workspace_path=workspace,
+        canonical_repo_root=ctx["canonical_repo_root"],
+        current_branch=git_state.get("current_branch"),
+        head_sha=git_state.get("head_sha"),
+        porcelain_status=git_state.get("porcelain_status") or "",
+        remote_master_sha=remote_master_sha,
+        task=task,
+    )
+
+
 def _enforce_branches_only_author_mutation(
     worktree_path: str | None = None,
     *,
     task: str | None = None,
+    bootstrap_assessment: Any = _BOOTSTRAP_UNSET,
 ) -> None:
     """#274: author file/branch mutations must run from a branches/ worktree.
 
@@ -859,27 +905,29 @@ def _enforce_branches_only_author_mutation(
         return
 
     # #749 create_issue bootstrap: narrow phase exemption only.
+    # #757: consume the caller-computed assessment when one was threaded in, so
+    # this guard and the later #604 anti-stomp guard judge identical evidence.
+    # Falling back to computing it here preserves behaviour for callers that
+    # supply none.
     import create_issue_bootstrap as _cib
 
-    remote_master_sha = None
-    try:
-        remote_master_sha = root_checkout_guard.resolve_remote_master_sha(
-            ctx["canonical_repo_root"]
-        )
-    except Exception:
-        remote_master_sha = None
-    bootstrap = _cib.assess_create_issue_bootstrap(
+    bootstrap = (
+        _create_issue_bootstrap_assessment(task, worktree_path)
+        if bootstrap_assessment is _BOOTSTRAP_UNSET
+        else bootstrap_assessment
+    )
+    if _cib.bootstrap_permits_control_checkout(
+        bootstrap,
+        task=task,
         workspace_path=workspace,
         canonical_repo_root=ctx["canonical_repo_root"],
-        current_branch=git_state.get("current_branch"),
-        head_sha=git_state.get("head_sha"),
-        porcelain_status=git_state.get("porcelain_status") or "",
-        remote_master_sha=remote_master_sha,
-        task=task,
-    )
-    if bootstrap.get("allowed"):
+    ):
         return
-    if bootstrap.get("block") and not bootstrap.get("not_applicable"):
+    if (
+        isinstance(bootstrap, dict)
+        and bootstrap.get("block")
+        and not bootstrap.get("not_applicable")
+    ):
         raise RuntimeError(_cib.format_create_issue_bootstrap_error(bootstrap))
     raise RuntimeError(
         author_mutation_worktree.format_author_mutation_worktree_error(assessment)
@@ -926,6 +974,7 @@ def _run_anti_stomp_preflight(
     workflow_hash_valid: bool | None = None,
     workflow_hash_reasons: list[str] | None = None,
     raise_on_block: bool = True,
+    bootstrap_assessment: Any = _BOOTSTRAP_UNSET,
 ) -> dict | None:
     """Shared #604 anti-stomp preflight for MCP mutation entrypoints.
 
@@ -1106,6 +1155,14 @@ def _run_anti_stomp_preflight(
         source_contaminated=source_contaminated,
         contamination_reasons=contamination_reasons,
         manual_bypass_attempted=False,
+        # #757: same server-derived bootstrap decision the #274 guard consumed.
+        # Computing it here when unsupplied keeps standalone callers consistent
+        # rather than silently bootstrap-blind.
+        create_issue_bootstrap_assessment=(
+            _create_issue_bootstrap_assessment(task, worktree_path)
+            if bootstrap_assessment is _BOOTSTRAP_UNSET
+            else bootstrap_assessment
+        ),
     )
     if not assessment.get("block"):
         return None
@@ -1248,7 +1305,12 @@ def verify_preflight_purity(
         # Historical path: root + branches after purity-order when dirty paths live.
         _enforce_canonical_repository_root(worktree_path, remote=remote)
         _enforce_root_checkout_guard(worktree_path)
-        _enforce_branches_only_author_mutation(worktree_path, task=task)
+        # #757: compute the create_issue bootstrap decision ONCE and hand the
+        # same result to both the #274 and #604 guards, so they cannot disagree.
+        bootstrap_assessment = _create_issue_bootstrap_assessment(task, worktree_path)
+        _enforce_branches_only_author_mutation(
+            worktree_path, task=task, bootstrap_assessment=bootstrap_assessment
+        )
         _enforce_issue_scope_guard(
             worktree_path,
             task=task,
@@ -1258,6 +1320,7 @@ def verify_preflight_purity(
         # #604: common anti-stomp preflight after legacy + #683 enforcers.
         _run_anti_stomp_preflight(
             task,
+            bootstrap_assessment=bootstrap_assessment,
             remote=remote,
             worktree_path=worktree_path,
             org=org,
@@ -1282,7 +1345,11 @@ def verify_preflight_purity(
     if production_active:
         _enforce_canonical_repository_root(worktree_path, remote=remote)
         _enforce_root_checkout_guard(worktree_path)
-        _enforce_branches_only_author_mutation(worktree_path, task=task)
+        # #757: one shared bootstrap decision for both guards (see above).
+        bootstrap_assessment = _create_issue_bootstrap_assessment(task, worktree_path)
+        _enforce_branches_only_author_mutation(
+            worktree_path, task=task, bootstrap_assessment=bootstrap_assessment
+        )
         _enforce_issue_scope_guard(
             worktree_path,
             task=task,
@@ -1292,6 +1359,7 @@ def verify_preflight_purity(
         if force_anti_stomp:
             _run_anti_stomp_preflight(
                 task,
+                bootstrap_assessment=bootstrap_assessment,
                 remote=remote,
                 worktree_path=worktree_path,
                 org=org,