docs(changelog): record the four unreleased user-facing fixes before the release

[jpr5]

Adds the four user-facing [Unreleased] CHANGELOG entries that landed since the v1.38.0 tag but had no entry, so the release notes are complete before the version is cut.

Docs-only: git diff --name-only origin/main..HEAD is CHANGELOG.md and nothing else. Version-neutral — no bump, so it does not trigger publish-release.yml. Merge it before the release bump, or lift the text into the release commit; either works.

Each entry was written from the actual commit diff, not the subject line:

• AG-UI usage on RUN_FINISHED/RUN_ERROR — aa68b26 (fix(drift): classify the new Gemini families, and document the procedure that actually applies one #378): the new optional usage?: AGUITokenUsage[], typed and emitted, numeric-only, emitted only when supplied.
• Responses-API function-call collapse → toolCalls — 23a8c3c / fix: collapse OpenAI Responses-API function-call streams into toolCalls #380: a tool-call-only Responses turn previously collapsed to empty content; now accumulates into toolCalls keyed by output_index, capturing call_id.
• Gemini Live speak-and-call ordering — a7d9b64 (fix(drift): classify the new Gemini families, and document the procedure that actually applies one #378): a serverContent (audio + text companion) strictly before the toolCall, then turnComplete; audio turns keep their companions.
• CLI signal handlers before readiness — 1079b46 (fix(drift): attribute a WS refusal, close the CLI signal race, and probe a modality Gemini serves #374): SIGINT/SIGTERM registered before the readiness log, closing the window where a supervisor's SIGTERM killed the process ungracefully (55/60 → 0/60). The residual — a signal strictly before readiness — is stated in the entry, drawn from code placement rather than a documented commit note.

Verified: prettier clean, commitlint RC 0, no version-bearing file touched.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@copilotkit/aimock@381

commit: 0bfd907

[contextablemark]

looks good