fix: clean up main abort listeners

[JustYannicc]

What changed

• Added idempotent cleanup/finalize paths for src/main/ai-provider.ts HTTP requests and Whisper uploads so tracked abort listeners are removed on success, HTTP error, request error, and explicit abort.
• Kept streaming cancellation semantics for 2xx AI responses by retaining the HTTP abort listener until the response stream ends/closes/errors.
• Updated the ollama-pull main-process handler to use a named abort listener and centralized finalizer for request-map and listener cleanup.
• Extended provider/Ollama tests with tracked AbortSignal add/remove counts and a narrow main-process Ollama source guard.

Why

Long-running AI and Ollama paths reused caller-owned abort signals while lower-level helpers attached inline one-shot listeners. Successful and failed requests could leave listener closures attached until the caller signal was garbage collected, and abort/error races had no shared cleanup path.

Compatibility impact

Behavior is intended to be preserving: cancellation still uses the existing Request aborted and Transcription aborted errors, HTTP error messages are unchanged, and Ollama aborts still suppress user-facing pull errors when the controller is aborted.

How tested

• node --test scripts/test-ai-provider-gemini-prompt-streaming.mjs
• node --test scripts/test-ai-provider-whisper-upload.mjs
• node --test scripts/test-ollama-pull-listener-cleanup.mjs
• pnpm run build:main
• pnpm run typecheck:renderer
• Codex LSP diagnostics on src/main/ai-provider.ts and src/main/main.ts: no diagnostics found.

Performance evidence

• HTTP helper before: successful, HTTP-error, and request-error requests retained one abort listener on the caller signal. After: tracked counts balance to adds=1 removes=1 active=0 for success, HTTP error, request error, and abort; during a successful streaming response the listener remains active after headers (adds=1 removes=0 active=1) and is removed when the stream completes (adds=1 removes=1 active=0).
• Whisper upload before: success/error/abort paths had no shared removal path for the upload abort listener. After: success, HTTP error, request error, and mid-flight abort each end at adds=1 removes=1 active=0; pre-aborted requests remain adds=0 removes=0 active=0.
• Ollama pull renderer baseline remains documented by the existing test: before remount cleanup listener counts were progress=6 done=6 error=6; after cleanup they are progress=0 done=0 error=0. The new main-process guard verifies ollama-pull uses a named onAbort, calls removeEventListener, and centralizes active request deletion in finishPullRequest().

Stack validation

• Started from 206eab8280a2eb91a57e4e74ea6df99e45a55cb4 on codex/perf-wave3-integration-stack-20260704 lineage.
• Branch: codex/perf-wave4-main-abort-listeners.
• No coordinator markdown, playbooks, prompts, or generated lockfiles are included.

Replaces

None.

[JustYannicc]

Closing in favor of #601, which fully replaces this granular PR in the wave4 runtime/main consolidation. Literal validation now passes with /opt/homebrew/opt/node@22/bin/npm run build:main, and #601 is ready for review.