feat: operation-name normalization table with fail-closed enforcement (#106)

Promote the #103 minimal alias map to the documented public table
GITEA_OPERATION_ALIASES and add the #106 enforcement layer:

- normalize_operation(op, service): canonical namespaced names; legacy
  spellings accepted only via the explicit table; unknown, ambiguous,
  and cross-service names fail closed.
- check_operation(op, allowed, forbidden, service): normalizes BOTH the
  requested operation and the profile lists before any membership
  check; forbidden always overrides allowed; unnormalizable allowed
  entries grant nothing and unnormalizable forbidden entries deny the
  request, so normalization can never silently widen permissions;
  empty/missing allowed list denies everything.
- gitea_check_pr_eligibility now routes its capability check through
  check_operation, fixing the mismatch where canonical namespaced
  profile ops (gitea.pr.merge) never matched the raw action (merge)
  and namespaced forbidden entries were never enforced.
- Document the normalization table and enforcement rules in
  docs/gitea-execution-profiles.md, replacing the stale 'enforcement
  out of scope' caveat.
- tests/test_op_normalization.py: full #106 matrix (27 tests) —
  qualified/legacy allowed and forbidden, unknown, ambiguous, service
  mismatch, forbidden-overrides-allowed, empty/missing allowed,
  duplicates after normalization, no permission widening, and
  eligibility integration proving normalization happens before
  enforcement. Existing v1/env unqualified behaviour stays compatible.

Closes #106

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

mcp_server.py

@@ -521,14 +521,24 @@ def gitea_check_pr_eligibility(
         return result
 
     # Profile capability check (metadata only; not enforcement of the action).
+    # Both the action and the profile lists are normalized before comparison
+    # (#106), so legacy spellings ("merge") and canonical namespaced ops
+    # ("gitea.pr.merge") always match each other and never cross services.
     allowed = profile["allowed_operations"]
     forbidden = profile["forbidden_operations"]
-    if not allowed:
-        reasons.append("profile has no configured allowed operations (fail closed)")
-    if action in forbidden:
-        reasons.append(f"profile forbids '{action}'")
-    elif action not in allowed:
-        reasons.append(f"profile is not allowed to {action}")
+    op_ok, op_reason = gitea_config.check_operation(action, allowed, forbidden)
+    if not op_ok:
+        if op_reason == "no-allowed-operations":
+            reasons.append(
+                "profile has no configured allowed operations (fail closed)")
+        elif op_reason == "forbidden":
+            reasons.append(f"profile forbids '{action}'")
+        elif op_reason == "invalid-forbidden-entry":
+            reasons.append(
+                "profile has an unrecognized forbidden operation entry "
+                "(fail closed)")
+        else:
+            reasons.append(f"profile is not allowed to {action}")
 
     h, o, r = _resolve(remote, host, org, repo)