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_load_session_cli.py

@@ -92,13 +92,17 @@ class TestOutputFormatFlagParity:
         )
         assert result.returncode == 0
         data = json.loads(result.stdout)
-        assert data == {
-            'session_id': 'gamma',
-            'loaded': True,
-            'messages_count': 2,
-            'input_tokens': 5,
-            'output_tokens': 7,
-        }
+        # Verify common envelope fields (SCHEMAS.md contract)
+        assert 'timestamp' in data
+        assert data['command'] == 'load-session'
+        assert data['exit_code'] == 0
+        assert data['schema_version'] == '1.0'
+        # Verify command-specific fields
+        assert data['session_id'] == 'gamma'
+        assert data['loaded'] is True
+        assert data['messages_count'] == 2
+        assert data['input_tokens'] == 5
+        assert data['output_tokens'] == 7
 
     def test_text_mode_unchanged_on_success(self, tmp_path: Path) -> None:
         """Legacy text output must be byte-identical for backward compat."""