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>

config/providers.yaml

@@ -25,10 +25,13 @@ providers:
     url: "http://localhost:11434"
     models:
       # Text + Tools models
-      - name: llama3.1:8b-instruct
+      - name: qwen3.5:latest
         default: true
         context_window: 128000
         capabilities: [text, tools, json, streaming]
+      - name: llama3.1:8b-instruct
+        context_window: 128000
+        capabilities: [text, tools, json, streaming]
       - name: llama3.2:3b
         context_window: 128000
         capabilities: [text, tools, json, streaming, vision]
@@ -115,6 +118,7 @@ fallback_chains:
   
   # General text generation (any model)
   text:
+    - qwen3.5:latest
     - llama3.1:8b-instruct
     - qwen2.5:14b
     - deepseek-r1:1.5b