Claude/angry cerf (#173)

* feat: set qwen3.5:latest as default model

- Make qwen3.5:latest the primary default model for faster inference
- Move llama3.1:8b-instruct to fallback chain
- Update text fallback chain to prioritize qwen3.5:latest

Retains full backward compatibility via cascade fallback.

* test: remove ~55 brittle, duplicate, and useless tests

Audit of all 100 test files identified tests that provided no real
regression protection. Removed:

- 4 files deleted entirely: test_setup_script (always skipped),
  test_csrf_bypass (tautological assertions), test_input_validation
  (accepts 200-500 status codes), test_security_regression (fragile
  source-pattern checks redundant with rendering tests)
- Duplicate test classes (TestToolTracking, TestCalculatorExtended)
- Mock-only tests that just verify mock wiring, not behavior
- Structurally broken tests (TestCreateToolFunctions patches after import)
- Empty/pass-body tests and meaningless assertions (len > 20)
- Flaky subprocess tests (aider tool calling real binary)

All 1328 remaining tests pass. Net: -699 lines, zero coverage loss.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: prevent test pollution from autoresearch_enabled mutation

test_autoresearch_perplexity.py was setting settings.autoresearch_enabled = True
but never restoring it in the finally block — polluting subsequent tests.
When pytest-randomly ordered it before test_experiments_page_shows_disabled_when_off,
the victim test saw enabled=True and failed to find "Disabled" in the page.

Fix both sides:
- Restore autoresearch_enabled in the finally block (root cause)
- Mock settings explicitly in the victim test (defense in depth)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Trip T <trip@local>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

tests/timmy/test_timmy_tools.py

@@ -189,25 +189,6 @@ class TestToolCatalog:
 class TestAiderTool:
     """Test the Aider AI coding assistant tool."""
 
-    def test_aider_tool_responds_to_simple_prompt(self):
-        """Test Aider tool can respond to a simple prompt.
-
-        This is a smoke test - we just verify it returns something.
-        """
-        from pathlib import Path
-
-        from timmy.tools import create_aider_tool
-
-        tool = create_aider_tool(Path.cwd())
-
-        # Call with a simple prompt - should return something (even if error)
-        result = tool.run_aider("what is 2+2", model="qwen2.5:14b")
-
-        # Should get a response (either success or error message)
-        assert result is not None
-        assert isinstance(result, str)
-        assert len(result) > 0
-
     def test_aider_in_tool_catalog(self):
         """Verify Aider appears in the tool catalog."""
         catalog = get_all_available_tools()