feat(adapters): reassemble Anthropic responses

[kev1n77]

Summary

• add a provider-neutral ResponseTrace to Prompt IR with JSON and StreamEvent evidence
• reassemble Anthropic Messages and legacy Complete JSON/SSE responses, including text, thinking, tool input fragments, cumulative usage, stop metadata, unknown events, cancellation, and error streams
• refresh Prompt IR after response persistence and expose ordered stream milestones in the desktop Timeline without inventing timestamps
• keep response output outside prompt full-text search and update schemas, bindings, golden fixtures, and progress docs

Verification

• cargo fmt --all -- --check
• cargo test --workspace --all-targets
• cargo clippy --workspace --all-targets -- -D warnings
• cargo fmt --manifest-path apps/desktop/src-tauri/Cargo.toml -- --check
• cargo test --manifest-path apps/desktop/src-tauri/Cargo.toml
• cargo clippy --manifest-path apps/desktop/src-tauri/Cargo.toml --all-targets -- -D warnings
• npm run desktop:check
• npm run desktop:build
• python -m unittest discover -s sidecars/mitmproxy/tests -v