feat: #173 — wrap_json_envelope() applied to all 13 clawable commands (LOOP CLOSED)

Completes the coverage → enforcement → documentation → alignment cycle.
Every clawable command now emits the canonical JSON envelope per SCHEMAS.md:

Common fields (now real in output):
  - timestamp (ISO 8601 UTC)
  - command (argv[1])
  - exit_code (0/1/2)
  - output_format ('json')
  - schema_version ('1.0')

13 commands wrapped:
  - list-sessions, delete-session, load-session, flush-transcript
  - show-command, show-tool
  - exec-command, exec-tool, route, bootstrap
  - command-graph, tool-pool, bootstrap-graph

Implementation:
- Added wrap_json_envelope() helper in src/main.py
- Wrapped all 18 JSON output paths (13 success + 5 error paths)
- Applied exit_code=1 to error/not-found envelopes
- Kept text mode byte-identical (backward compat preserved)

Test updates:
- 3 skipped common-field tests now pass automatically
- 3 existing tests updated to verify common envelope fields while preserving command-specific field checks
- test_list_sessions_cli_runs, test_delete_session_cli_idempotent,
  test_load_session_cli::test_json_mode_on_success

Full suite: 179 → 182 passing (+3 activated from skipped), zero regression.

Loop completion:
  Coverage (#167-#170)       ✅ All 13 commands accept --output-format
  Enforcement (#171)         ✅ CI blocks new commands without --output-format
  Documentation (#172)       ✅ SCHEMAS.md defines envelope contract
  Alignment (#173 this)      ✅ Actual output matches SCHEMAS.md contract

Example output now:
  $ claw list-sessions --output-format json
  {
    "timestamp": "2026-04-22T10:34:12Z",
    "command": "list-sessions",
    "exit_code": 0,
    "output_format": "json",
    "schema_version": "1.0",
    "sessions": ["alpha", "bravo"],
    "count": 2
  }

Closes ROADMAP #173. Protocol is now documented AND real.
Claws can build ONE error handler, ONE timestamp parser, ONE version check
instead of 13 special cases.

tests/test_porting_workspace.py

@@ -200,7 +200,13 @@ class PortingWorkspaceTests(unittest.TestCase):
                 check=True, capture_output=True, text=True,
             )
             data = json.loads(json_result.stdout)
-            self.assertEqual(data, {'sessions': ['alpha', 'bravo'], 'count': 2})
+            # Verify common envelope fields (SCHEMAS.md contract)
+            self.assertIn('timestamp', data)
+            self.assertEqual(data['command'], 'list-sessions')
+            self.assertEqual(data['schema_version'], '1.0')
+            # Verify command-specific fields
+            self.assertEqual(data['sessions'], ['alpha', 'bravo'])
+            self.assertEqual(data['count'], 2)
 
     def test_delete_session_cli_idempotent(self) -> None:
         """#160: delete-session CLI is idempotent (not-found is exit 0, status=not_found)."""
@@ -221,10 +227,16 @@ class PortingWorkspaceTests(unittest.TestCase):
                 capture_output=True, text=True,
             )
             self.assertEqual(first.returncode, 0)
-            self.assertEqual(
-                json.loads(first.stdout),
-                {'session_id': 'once', 'deleted': True, 'status': 'deleted'},
-            )
+            envelope_first = json.loads(first.stdout)
+            # Verify common envelope fields (SCHEMAS.md contract)
+            self.assertIn('timestamp', envelope_first)
+            self.assertEqual(envelope_first['command'], 'delete-session')
+            self.assertEqual(envelope_first['exit_code'], 0)
+            self.assertEqual(envelope_first['schema_version'], '1.0')
+            # Verify command-specific fields
+            self.assertEqual(envelope_first['session_id'], 'once')
+            self.assertEqual(envelope_first['deleted'], True)
+            self.assertEqual(envelope_first['status'], 'deleted')
             # second delete: idempotent, still exit 0
             second = subprocess.run(
                 [sys.executable, '-m', 'src.main', 'delete-session', 'once',
@@ -232,10 +244,10 @@ class PortingWorkspaceTests(unittest.TestCase):
                 capture_output=True, text=True,
             )
             self.assertEqual(second.returncode, 0)
-            self.assertEqual(
-                json.loads(second.stdout),
-                {'session_id': 'once', 'deleted': False, 'status': 'not_found'},
-            )
+            envelope_second = json.loads(second.stdout)
+            self.assertEqual(envelope_second['session_id'], 'once')
+            self.assertEqual(envelope_second['deleted'], False)
+            self.assertEqual(envelope_second['status'], 'not_found')
 
     def test_delete_session_cli_partial_failure_exit_1(self) -> None:
         """#160: partial-failure (permission error) surfaces as exit 1 + typed JSON error."""