feat(capability_matrix): add 12 v2 fields to VendorCapabilities

The 7 v1 fields (vision, tool_calling, caching, streaming,
model_discovery, context_window, cost_tracking) plus 2 cost
fields and notes are now extended by 12 v2 fields:

  local, reasoning, structured_output, code_execution,
  web_search, x_search, file_search, mcp_support,
  audio, video, grounding, computer_use

All default to False. Registry entries continue to work
unchanged (backward compatible). t4_1 of Phase 4.

Tests:
- 12 parameterized 'default is False' tests
- 12 parameterized 'round-trip to True' tests
- 3 'local flag' tests: per-model, wildcard fallback,
  vendor isolation
- 3 pre-existing registry tests still pass
- 96/96 vendor+tool+provider+import-isolation tests pass
  (no regressions; +27 new tests this commit)

src/vendor_capabilities.py

@@ -15,6 +15,19 @@ class VendorCapabilities:
  cost_input_per_mtok: float = 0.0
  cost_output_per_mtok: float = 0.0
  notes: str = ''
+ # v2 fields (added 2026-06-11)
+ local: bool = False
+ reasoning: bool = False
+ structured_output: bool = False
+ code_execution: bool = False
+ web_search: bool = False
+ x_search: bool = False
+ file_search: bool = False
+ mcp_support: bool = False
+ audio: bool = False
+ video: bool = False
+ grounding: bool = False
+ computer_use: bool = False
 
 _REGISTRY: dict[tuple[str, str], VendorCapabilities] = {}