perf(runtime): consolidate extension lifecycle and media fixes

[JustYannicc]

What changed

• Consolidates wave4 runtime/main/build/media fixes onto latest origin/main.
• Reuses fresh extension command bundles with build stamps and stale-command detection.
• Refreshes installed extension commands without rediscovering app/settings/script/quicklink commands.
• Cleans extension spawned process lifecycle by renderer sender and clears registry-scoped child processes on ExtensionView teardown.
• Adds abort-aware extension fetch proxy request IDs and async HTTP response decoding.
• Cleans main abort listeners for AI provider requests and Ollama pull requests.
• Streams cloud media uploads/downloads to avoid full Buffer concatenation for STT/TTS paths.
• Guards Raycast action/list/grid/menubar registry microtasks after unmount.

Why

• The individual wave PRs overlap in the same main/runtime surfaces, making review order and duplicate cleanup harder than the underlying changes warrant.
• A single consolidation keeps the extension install/update/build flow compatible with docs/extension-install-flow.md while giving reviewers one branch to validate.

Compatibility impact

• No feature trimming.
• Raycast built-in/package facades are preserved; child_process remains routed through the SuperCmd facade so child processes can be tracked and cleaned per extension view.
• Extension fetch keeps native fallback behavior for unsupported bodies and non-HTTP URLs.
• Provider behavior is preserved while media buffers are streamed instead of concatenated.

How tested

• node --test scripts/test-extension-runner-multi-command-build.mjs (13 pass, 1 measurement skip)
• node --test scripts/test-extension-command-refresh-cache.mjs
• node --test scripts/test-extension-fetch-proxy-abort.mjs scripts/test-http-response-decode-async.mjs
• node --test scripts/test-cloud-media-buffering.mjs
• node --test scripts/test-registry-microtask-lifecycle.mjs
• node node_modules/typescript/bin/tsc -p tsconfig.main.json --noEmit --pretty false
• Direct build:main equivalent: node node_modules/typescript/bin/tsc -p tsconfig.main.json --pretty false, then copied src/main/emoji-data.json to dist/main/emoji-data.json
• Codex LSP diagnostics: no errors in touched TypeScript/TSX files.
• Dependency restore for literal package script: /opt/homebrew/opt/node@22/bin/npm ci --ignore-scripts --force --no-audit --no-fund
• Literal package script: /opt/homebrew/opt/node@22/bin/npm run build:main
• Renderer-wide tsc -p tsconfig.renderer.json --noEmit still reports existing unrelated project errors; touched renderer files are LSP-clean.

Performance evidence

• Extension build cache: unchanged 5-command fixture reuses 5/5 bundles; a single edited command rebuilds 1/5 bundles; 1/5/20-command fixtures batch into one esbuild call each.
• Extension refresh benchmark: legacy path performed 40 structural discovery starts, targeted refresh performed 0 structural discovery starts and 40 extension-only starts; median refresh improved from 12.041 ms to 1.674 ms in the local harness.
• HTTP decode harness: async gzip decode preserved output and reduced timer delay from 3.691 ms sync to 0.613 ms async in the fixture.
• Cloud media harness: ElevenLabs STT avoided a 6,291,864 byte multipart body copy, Mistral Voxtral STT avoided a 7,340,475 byte multipart body copy, and ElevenLabs TTS streamed 5,767,168 bytes directly to the temp file without retaining a full response Buffer.
• Registry lifecycle harness: action/list/grid/menubar post-unmount setState calls reproduced at 1 each in the legacy scheduler and dropped to 0 each after the guard.

Stack validation

• Branch is based directly on latest origin/main (9bdd3d2) rather than the integration stack.
• Inspected older consolidated PRs perf(runtime): reduce extension and menubar churn #530, perf(ai): batch streaming and status updates #531, perf(mac): reduce native polling and async IO stalls #534, perf(search): reduce indexing and ranking overhead #535, perf(ai): reduce streaming and native media overhead #556, perf(runtime): reduce extension lifecycle and icon churn #558, perf(commands): reduce command and file refresh overhead #573, and perf(runtime): reduce lifecycle and media churn #575; this PR does not supersede them because it only carries wave4 tip deltas onto origin/main.
• Adjacent form snapshot PRs fix: clear form snapshots on unmount #582, fix: clear form runtime snapshots on unmount #596, and fix: clear form snapshots on unmount #597 are intentionally left out because they are outside the requested main/runtime/media/build consolidation group.
• Registry duplicate PRs fix(raycast): guard registry microtasks after unmount #584, fix: guard registry microtasks after unmount #595, and fix(raycast): guard registry microtask teardown #598 were already closed before this draft was opened; their covered changes are included here for provenance.

Replaces

• fix(raycast): guard registry microtasks after unmount #584
• fix: clean up extension spawn lifecycle #585
• perf: target extension command refresh #586
• fix: cancel extension fetch proxy requests #587
• fix: clean up main abort listeners #590
• perf: stream cloud media buffers #593
• perf: reuse stale extension command builds #594
• fix: guard registry microtasks after unmount #595
• fix(raycast): guard registry microtask teardown #598

[JustYannicc]

Superseded by the consolidated runtime/lifecycle/media PR: #622