fix(session): require config-backed mutation authority and workspace-bound targets (#714)

Close the #714 remediation gap left at 943d402 where env-only mutation
profiles, REMOTES Timesheet defaults treated as explicit caller input, and
machine-dependent Git remotes produced false greens.

- Fail closed when mutations lack a config-backed profile with non-empty
  allowed_repositories; env ops cannot invent mutation authority.
- Preserve omitted-vs-explicit org/repo provenance through the mutation
  gate; omitted targets bind to the verified workspace repository.
- Prefer workspace-aligned Git remotes over historical Timesheet defaults
  in MCP _resolve and CLI resolve_remote.
- Centralize deterministic config-backed mutation fixtures; migrate
  mutation tests off env-only authority without weakening security
  assertions.

Full suite: 2744 passed, 6 skipped.

tests/test_operation_scoped_roles.py

@@ -40,6 +40,7 @@ CONFIG_TEST = {
             "auth": {"type": "env", "name": "GITEA_TOKEN_AUTHOR"},
             "allowed_operations": ["gitea.read", "gitea.issue.create", "gitea.pr.create", "gitea.branch.push", "gitea.issue.comment"],
             "forbidden_operations": ["gitea.pr.approve", "gitea.pr.merge"],
+            "allowed_repositories": ["Scaled-Tech-Consulting/Gitea-Tools", "913443/eAgenda"],
             "execution_profile": "author-profile"
         },
         "reviewer-profile": {
@@ -51,6 +52,7 @@ CONFIG_TEST = {
             "auth": {"type": "env", "name": "GITEA_TOKEN_REVIEWER"},
             "allowed_operations": ["gitea.read", "gitea.pr.review", "gitea.pr.approve", "gitea.pr.merge", "gitea.issue.comment"],
             "forbidden_operations": ["gitea.pr.create", "gitea.branch.push"],
+            "allowed_repositories": ["Scaled-Tech-Consulting/Gitea-Tools", "913443/eAgenda"],
             "execution_profile": "reviewer-profile"
         }
     }
@@ -65,6 +67,15 @@ class TestOperationScopedRoles(unittest.TestCase):
         })
         self._remotes_patch.start()
         mcp_server._IDENTITY_CACHE.clear()
+        self._url = patch.object(
+            mcp_server,
+            "_local_git_remote_url",
+            side_effect=lambda n: {
+                "prgs": "https://gitea.prgs.cc/Scaled-Tech-Consulting/Gitea-Tools.git",
+                "dadeschools": "https://gitea.dadeschools.net/913443/eAgenda.git",
+            }.get(n),
+        )
+        self._url.start()
         gitea_config._active_profile_override = None
         mcp_server._MUTATION_AUTHORITY = None
         self._dir = tempfile.TemporaryDirectory()
@@ -72,6 +83,11 @@ class TestOperationScopedRoles(unittest.TestCase):
         self._write_config(CONFIG_TEST)
 
     def tearDown(self):
+        try:
+            self._url.stop()
+        except Exception:
+            pass
+
         self._remotes_patch.stop()
         mcp_server._IDENTITY_CACHE.clear()
         gitea_config._active_profile_override = None