Aimock fixture load order is shared -> d4 -> d6, and matching is first-match-wins. A
broad d4 langgraph-python chat fixture for search_flights was shadowing the d6
beautiful-chat fixture and preventing the intended response from firing. Neutered the
d4 matcher to a non-matching sentinel so the d6 fixture wins.
Also refreshed d6/tool-rendering-custom-catchall.json and d6/tool-rendering.json:
replaced fragile turnIndex:0 gates with hasToolResult:false so the AAPL first-leg
fixture fires correctly when D5 probes run a prior 'weather in Tokyo' pill in the
same thread (multi-pill turnIndex>=2).
LGP D6 now passes 185/0/2 locally (2 skips are the by-design mcp-apps iframe gap).
Adds per-integration D6 fixtures for langgraph-python, langgraph-typescript,
and langgraph-fastapi. Each fixture is keyed by match.context for cross-
integration isolation and uses hasToolResult:false on toolCall responses
to prevent re-match loops.