Implemented the next parity slice: prompt-budget preflight and context collapse.

Core changes:

  - Added claw-code/src/token_budget.py for projected prompt size, chat-framing overhead, output reserve, and soft/hard input limits.
  - Wired preflight prompt-length validation and auto-compact/context collapse into claw-code/src/agent_runtime.py.
  - Extended claw-code/src/compact.py so compaction reports usage back to the runtime.
  - Added inspection surfaces in claw-code/src/agent_slash_commands.py and claw-code/src/main.py:
      - /token-budget and /budget
      - token-budget
  - Hardened claw-code/src/tokenizer_runtime.py so arbitrary simple model names fall back cleanly instead of trying a slow Transformers
    lookup.
  - Exported the new helpers in claw-code/src/__init__.py.

  Docs and tracking:

  - Updated claw-code/PARITY_CHECKLIST.md to mark prompt-length validation, token-budget calculation, and auto-compact/context collapse as
    done.
  - Updated claw-code/README.md and claw-code/TESTING_GUIDE.md with the new commands and behavior.

  Tests:

  - Added claw-code/tests/test_token_budget.py.
  - Updated claw-code/tests/test_agent_runtime.py, claw-code/tests/test_agent_slash_commands.py, claw-code/tests/test_main.py, and claw-code/
    tests/test_agent_context_usage.py.
  - Verified with:
      - /data/fs201059/aa17626/miniconda3/bin/python3 -m compileall src tests
      - /data/fs201059/aa17626/miniconda3/bin/python3 -m unittest -v tests.test_token_budget
        tests.test_agent_runtime.AgentRuntimeTests.test_agent_rejects_prompt_before_backend_when_preflight_input_budget_is_exceeded
        tests.test_agent_runtime.AgentRuntimeTests.test_agent_auto_compacts_context_before_next_model_call tests.test_agent_slash_commands
        tests.test_main tests.test_compact tests.test_tokenizer_runtime tests.test_agent_context_usage
      - Result: 71 tests, OK

tests/test_main.py

@@ -104,6 +104,8 @@ class MainCliTests(unittest.TestCase):
                     [
                         'agent-chat',
                         'First prompt',
+                        '--model',
+                        'test-model',
                         '--cwd',
                         str(workspace),
                     ]
@@ -196,6 +198,21 @@ class MainCliTests(unittest.TestCase):
         self.assertEqual(args.key_path, 'review.mode')
         self.assertEqual(args.cwd, '.')
 
+    def test_parser_accepts_lsp_runtime_commands(self) -> None:
+        parser = build_parser()
+        args = parser.parse_args(['lsp-definition', 'sample.py', '4', '12', '--cwd', '.'])
+        self.assertEqual(args.command, 'lsp-definition')
+        self.assertEqual(args.file_path, 'sample.py')
+        self.assertEqual(args.line, 4)
+        self.assertEqual(args.character, 12)
+        self.assertEqual(args.cwd, '.')
+
+    def test_parser_accepts_token_budget_command(self) -> None:
+        parser = build_parser()
+        args = parser.parse_args(['token-budget', '--cwd', '.'])
+        self.assertEqual(args.command, 'token-budget')
+        self.assertEqual(args.cwd, '.')
+
     def test_parser_accepts_team_runtime_commands(self) -> None:
         parser = build_parser()
         args = parser.parse_args(['team-create', 'reviewers', '--member', 'alice', '--cwd', '.'])