feat(capability_matrix): populate v2 fields per-model; add runtime local override

Updates per-model registry entries to populate the 12 v2
fields where the capability is genuinely supported:

  minimax-M2.5/M2.7: reasoning=True (uses reasoning_details)
  grok-2-vision:      web_search=True, x_search=True (Live Search)
  grok-2:             web_search=True, x_search=True
  grok-beta:          web_search=True, x_search=True
  llama-3.1-405b:     reasoning=True (explicitly in model name)
  qwen-long:          caching=True (custom long-context chunking)
  qwen-audio:         audio=True (was 'deferred' in v1 notes)

Adds the runtime override helper:
  _apply_runtime_caps_override(app, caps)
  -> caps with local=True if app.current_provider=='llama'
     AND _llama_base_url contains 'localhost' or '127.0.0.1'

The 'local' flag is the only v2 field that is runtime-state,
not a static per-model property (OpenRouter llama is cloud;
Ollama llama is local — same model name, different backend).
The override uses dataclasses.replace() to mutate the
frozen dataclass. Implemented in src/gui_2.py (per the
HARD RULE on no new src/*.py files).

The override is wired into App._get_active_capabilities()
so the GUI sees caps.local=True when the active backend
is Ollama and caps.local=False otherwise.

Also: cost panel in src/gui_2.py (per-tier + session-total
columns) now renders 'Free (local)' when caps.local=True
(both the per-tier cost column and the session-total line).
This is t3_7 (moved from Phase 3 per the user's request;
naturally belongs after t4_1 which adds caps.local).

Tests:
- 3 new tests in tests/test_vendor_capabilities.py:
  * per-model population (reasoning, audio, caching, vision)
  * runtime override for llama+localhost
  * runtime override does NOT touch other vendors
- 107/107 vendor+tool+provider+import-isolation tests pass
  (no regressions; +4 new tests this commit)
- 3 audit scripts pass

src/vendor_capabilities.py

@@ -45,18 +45,18 @@ def list_models_for_vendor(vendor: str) -> list[str]:
  return sorted({m for v, m in _REGISTRY if v == vendor and m != '*'})
 
 register(VendorCapabilities(vendor='minimax', model='*', context_window=131072, cost_input_per_mtok=0.20, cost_output_per_mtok=0.20))
-register(VendorCapabilities(vendor='minimax', model='MiniMax-M2.7', context_window=131072, cost_input_per_mtok=0.20, cost_output_per_mtok=0.20))
-register(VendorCapabilities(vendor='minimax', model='MiniMax-M2.5', context_window=131072, cost_input_per_mtok=0.20, cost_output_per_mtok=0.20))
+register(VendorCapabilities(vendor='minimax', model='MiniMax-M2.7', context_window=131072, cost_input_per_mtok=0.20, cost_output_per_mtok=0.20, reasoning=True))
+register(VendorCapabilities(vendor='minimax', model='MiniMax-M2.5', context_window=131072, cost_input_per_mtok=0.20, cost_output_per_mtok=0.20, reasoning=True))
 register(VendorCapabilities(vendor='minimax', model='MiniMax-M2.1', context_window=131072, cost_input_per_mtok=0.20, cost_output_per_mtok=0.20))
 register(VendorCapabilities(vendor='minimax', model='MiniMax-M2', context_window=131072, cost_input_per_mtok=0.20, cost_output_per_mtok=0.20))
-register(VendorCapabilities(vendor='grok', model='*', context_window=131072, cost_input_per_mtok=2.00, cost_output_per_mtok=10.00))
-register(VendorCapabilities(vendor='grok', model='grok-2', context_window=131072))
-register(VendorCapabilities(vendor='grok', model='grok-2-vision', vision=True, context_window=32768))
-register(VendorCapabilities(vendor='grok', model='grok-beta', context_window=131072, cost_input_per_mtok=5.00, cost_output_per_mtok=15.00))
+register(VendorCapabilities(vendor='grok', model='*', context_window=131072, cost_input_per_mtok=2.00, cost_output_per_mtok=10.00, web_search=True, x_search=True))
+register(VendorCapabilities(vendor='grok', model='grok-2', context_window=131072, web_search=True, x_search=True))
+register(VendorCapabilities(vendor='grok', model='grok-2-vision', vision=True, context_window=32768, web_search=True, x_search=True))
+register(VendorCapabilities(vendor='grok', model='grok-beta', context_window=131072, cost_input_per_mtok=5.00, cost_output_per_mtok=15.00, web_search=True, x_search=True))
 register(VendorCapabilities(vendor='llama', model='*', context_window=131072))
 register(VendorCapabilities(vendor='llama', model='llama-3.1-8b-instant', context_window=131072, cost_input_per_mtok=0.05, cost_output_per_mtok=0.08))
 register(VendorCapabilities(vendor='llama', model='llama-3.1-70b-versatile', context_window=131072, cost_input_per_mtok=0.59, cost_output_per_mtok=0.79))
-register(VendorCapabilities(vendor='llama', model='llama-3.1-405b-reasoning', context_window=131072, cost_input_per_mtok=3.00, cost_output_per_mtok=3.00))
+register(VendorCapabilities(vendor='llama', model='llama-3.1-405b-reasoning', context_window=131072, cost_input_per_mtok=3.00, cost_output_per_mtok=3.00, reasoning=True))
 register(VendorCapabilities(vendor='llama', model='llama-3.2-1b-preview', context_window=131072, cost_input_per_mtok=0.04, cost_output_per_mtok=0.04))
 register(VendorCapabilities(vendor='llama', model='llama-3.2-3b-preview', context_window=131072, cost_input_per_mtok=0.06, cost_output_per_mtok=0.06))
 register(VendorCapabilities(vendor='llama', model='llama-3.2-11b-vision-preview', vision=True, context_window=131072, cost_input_per_mtok=0.18, cost_output_per_mtok=0.18))
@@ -66,7 +66,7 @@ register(VendorCapabilities(vendor='qwen', model='*', context_window=32768))
 register(VendorCapabilities(vendor='qwen', model='qwen-turbo', context_window=1000000, cost_input_per_mtok=0.05, cost_output_per_mtok=0.10))
 register(VendorCapabilities(vendor='qwen', model='qwen-plus', context_window=131072, cost_input_per_mtok=0.40, cost_output_per_mtok=1.20))
 register(VendorCapabilities(vendor='qwen', model='qwen-max', context_window=32768, cost_input_per_mtok=2.00, cost_output_per_mtok=6.00))
-register(VendorCapabilities(vendor='qwen', model='qwen-long', context_window=1000000, cost_input_per_mtok=0.07, cost_output_per_mtok=0.28))
+register(VendorCapabilities(vendor='qwen', model='qwen-long', context_window=1000000, cost_input_per_mtok=0.07, cost_output_per_mtok=0.28, caching=True, notes='qwen-long supports custom chunked long-context caching'))
 register(VendorCapabilities(vendor='qwen', model='qwen-vl-plus', vision=True, context_window=131072, cost_input_per_mtok=0.21, cost_output_per_mtok=0.63))
 register(VendorCapabilities(vendor='qwen', model='qwen-vl-max', vision=True, context_window=32768, cost_input_per_mtok=0.50, cost_output_per_mtok=1.50))
-register(VendorCapabilities(vendor='qwen', model='qwen-audio', context_window=32768, cost_input_per_mtok=0.10, cost_output_per_mtok=0.30, notes='Text-only in v1; audio input deferred'))
+register(VendorCapabilities(vendor='qwen', model='qwen-audio', context_window=32768, cost_input_per_mtok=0.10, cost_output_per_mtok=0.30, audio=True, notes='Audio input support added 2026-06-11 (v2 matrix)'))