feat: enforce live-namespace block in review/merge state machine (#543 AC5)

The namespace health check (05fdcee) classified a false-ready namespace but
only returned an advisory blocks_merge_workflow flag; nothing in the merge
gate consumed it. Wire it in so a broken live namespace hard-blocks merge.

- review_merge_state_machine.assess_workflow_blockers: add live_namespace_broken
  blocker (registered-in-FastMCP but not callable-through-namespace).
- assess_state_advancement: forward **blocker_kwargs so can_approve/can_merge/
  workflow_status honor the full blocker set (also fixes latent drop of
  mcp_reconnect_failed/stale_capability_state through those paths).
- gitea_assess_review_merge_state_machine tool: accept live_namespace_broken and
  thread it through all state-machine calls.
- Tests: prove can_merge/workflow_status/tool block on live_namespace_broken even
  with every review state + pre-merge gate satisfied; bridge classify verdict.
- Docs: enforcement section wiring blocks_merge_workflow -> live_namespace_broken.

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

tests/test_mcp_namespace_health.py

@@ -2,6 +2,7 @@ import unittest
 
 import gitea_mcp_server
 import mcp_namespace_health
+import review_merge_state_machine as rmsm
 
 
 class TestMcpNamespaceHealth(unittest.TestCase):
@@ -81,5 +82,74 @@ class TestMcpNamespaceHealth(unittest.TestCase):
         self.assertEqual(result["diagnostics"]["process_pid"], 9876)
 
 
+class TestLiveNamespaceBlocksMerge(unittest.TestCase):
+    """AC5: a broken live namespace must hard-block the review/merge state machine."""
+
+    def _merge_ready_completion(self):
+        # Completion through PRE_MERGE_RECHECK is the state where a clean merge
+        # is otherwise allowed (see test_merge_allowed_with_pre_merge_gates).
+        idx = rmsm.REVIEW_MERGE_STATES.index("PRE_MERGE_RECHECK")
+        return {state: True for state in rmsm.REVIEW_MERGE_STATES[: idx + 1]}
+
+    def _all_gates(self):
+        return {gate: True for gate in rmsm._PRE_MERGE_REQUIRED_GATES}
+
+    def test_assess_workflow_blockers_flags_live_namespace_broken(self):
+        clean = rmsm.assess_workflow_blockers()
+        self.assertFalse(clean["block"])
+
+        broken = rmsm.assess_workflow_blockers(live_namespace_broken=True)
+        self.assertTrue(broken["block"])
+        self.assertTrue(any("namespace" in r.lower() for r in broken["reasons"]))
+
+    def test_can_merge_blocks_even_when_all_gates_pass(self):
+        # Without the namespace blocker a fully-complete workflow can merge...
+        allowed = rmsm.can_merge(
+            self._merge_ready_completion(), pre_merge_gates=self._all_gates()
+        )
+        self.assertTrue(allowed["allowed"])
+
+        # ...but a broken live namespace overrides every satisfied gate.
+        blocked = rmsm.can_merge(
+            self._merge_ready_completion(),
+            pre_merge_gates=self._all_gates(),
+            live_namespace_broken=True,
+        )
+        self.assertTrue(blocked["block"])
+        self.assertFalse(blocked["allowed"])
+
+    def test_workflow_status_forwards_namespace_blocker(self):
+        status = rmsm.workflow_status(
+            self._merge_ready_completion(), live_namespace_broken=True
+        )
+        self.assertFalse(status["merge_allowed"])
+        self.assertFalse(status["approve_allowed"])
+
+    def test_server_tool_blocks_merge_on_live_namespace_broken(self):
+        result = gitea_mcp_server.gitea_assess_review_merge_state_machine(
+            state_completion=self._merge_ready_completion(),
+            pre_merge_gates=self._all_gates(),
+            live_namespace_broken=True,
+        )
+        self.assertTrue(result["blockers"]["block"])
+        self.assertFalse(result["merge"]["allowed"])
+
+    def test_classify_verdict_bridges_into_merge_block(self):
+        # The classify verdict is the intended feed for live_namespace_broken.
+        verdict = mcp_namespace_health.classify_namespace_probe(
+            "gitea-merger",
+            registered_tools=["gitea_whoami", "gitea_adopt_merger_pr_lease"],
+            probe_result={"success": False, "error": "client is closing: EOF"},
+            process={"pid": 555, "profile": "prgs-merger"},
+        )
+        self.assertTrue(verdict["blocks_merge_workflow"])
+        blocked = rmsm.can_merge(
+            self._merge_ready_completion(),
+            pre_merge_gates=self._all_gates(),
+            live_namespace_broken=verdict["blocks_merge_workflow"],
+        )
+        self.assertFalse(blocked["allowed"])
+
+
 if __name__ == "__main__":
     unittest.main()