- Add `ParsePluginExecutorResponseUsage` to extract token usage from non-streaming plugin responses across Claude, Gemini, Interactions, Antigravity, and OpenAI/Codex protocols.
- Add `ObservePluginExecutorStreamUsage` to observe and aggregate token usage across streaming chunks.
Closes: #5340
- add shared `EnsureResponsesUsageDetails` helper to patch `usage` objects with:
- `output_tokens_details.reasoning_tokens = 0`
- `input_tokens_details.cached_tokens = 0`
- for both plain JSON and SSE `data:` frames, including multi-line frames
- apply the helper to OpenAI Response format outputs in non-stream and stream paths across executors/plugins so translated payloads consistently include required usage details
- update websocket/completion payload builders to emit default `usage` detail fields for prewarm/finish responses
Closes: #4985
- Removed deprecated interceptor and executor-related methods, including `callRequestInterceptor`, `callResponseInterceptor`, and `callStreamChunkInterceptor`.
- Consolidated unused logic and pruned redundant imports to streamline `adapters.go`.
- No functional changes.
