fix(harness): resolve layer contradictions + context-budget caps for airouter TDD

- tdd-gate: pass criterion is the task's TEST_FILES scope (matches
  run-ci-tests.sh M19 P-14), not the full suite — contradicted
  qwen-code-methodology rule 5 in the same system prompt
- tdd-protect: tests/ path described relative to project working dir
  (AGENT_WORKING_DIR is /workspace/project in repo composites)
- qwen-code-methodology: task_complete tool DOES exist — rule 8 said
  the opposite; pytest examples use -q
- airouter-code-tdd template: TT-39 runtime_overrides
  (max_result_bytes 24KB, max_history_turns 16)

Claude-Session: https://claude.ai/code/session_012arAwUuBQrpnMzJ36mEVBk

harnesses/contexts/qwen-code-methodology/v1/CLAUDE.md

@@ -15,11 +15,11 @@ You are running on **Qwen3.6-27B** via the agentic tool-calling runner. Thinking
    If this shows deleted non-blank lines from existing code, you have broken something — revert and try again with a targeted `Edit`.
 5. **Only run the specific test file for your change.** Never run the full test suite.
    ```
-   python -m pytest tests/test_<module>.py -v --tb=short -x
+   python -m pytest tests/test_<module>.py -q --tb=short -x
    ```
 6. **Do not create backup copies** (`*_orig`, `*_old`, `*_bak`, `*_backup`).
 7. **Do not rename existing files before modifying them.**
-8. **When the task is done, respond with plain text and stop.** Do not call any tool to signal completion. There is no "finish", "done", or "report" tool — emitting one wastes a turn and the runner will treat it as more work.
+8. **When the task is done, call the `task_complete` tool once** (with a one-paragraph summary), or respond with plain text and stop. Do not invent other completion tools.
 
 ## How to work