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

task-templates/airouter-code-tdd.yaml

@@ -9,6 +9,10 @@ labels: [airouter]
 defaults:
   timeout: 3600
   max_turns: 100
+runtime_overrides:
+  # Context-budget controls (TT-39)
+  max_result_bytes: 24576
+  max_history_turns: 16
 pre_actions:
   - type: clone
     repo: "{{ repo_url }}"