[iLevyTate]

Summary

Fixes the known limitations listed on #51, plus a timing-fragile test that failed #52's macOS run.

• Driver version in the GPU backend record. GPUMonitor now asks nvidia-smi for name,memory.total,driver_version (Windows and Linux) and reads DriverVersion from Win32_VideoController on the WMI path, so gpu-backend-cache.json notices a driver update and the next launch re-runs the backend search. A missing or [N/A] third column leaves driverVersion out, so two-column output still parses. Linux without nvidia-smi (lspci) and macOS still report none.
• Embedding worker uses the same backend selection. With STRATOSORT_ENABLE_EMBEDDING_WORKER=true the worker thread ran its own full ladder (no supported-backend filter, no remembered backend). workerPools now passes { userDataPath, appVersion } as Piscina workerData; the worker passes getLlamaGpuTypes and a read-only view of the record (createReadOnlyLlamaBackendCache). Only LlamaService in the main process saves or clears the record, so the two stacks never race on the file; a failed read-only attempt logs Cached Llama backend failed; record left to its owner.
• No arm64 llama prebuilt in the x64 build (~11 MB). @node-llama-cpp/win-arm64 declares cpu: ["arm64", "x64"], so npm installs it on x64 runners. win.files now excludes !**/node_modules/@node-llama-cpp/win-!(${arch}|${arch}-*)/**; app-builder-lib expands ${arch} per packed arch (FileMatcher.normalizePattern), so x64 drops win-arm64 and arm64 (which inherits win.files via extends) drops any win-x64* package. Checked with app-builder-lib's own node_modules filter in electron-builder-config.test.js; verify-packaged-artifacts.js fails if a package for the other arch still holds files.
• Linux keeps the raster switches. Windows startup follow-ups: zip build, payload trim, relaunch during shutdown, sticky GPU fallback, backend cache #51 stopped appending enable-gpu-rasterization and enable-zero-copy everywhere. That stays on Windows and macOS (GPU raster is already Chromium's default there for non-blocklisted drivers), but Linux goes back to what every earlier release did, since its default varies with Chromium version and driver and the AppImage was never measured without them. Software mode appends neither.
• Deterministic health-check tests. healthCheckUtils.test.js › resets failures on successful check slept 20 ms on a real timer against a 30 ms interval and expected exactly one failure; on Explain why a zip copy cannot update instead of "Failed to check for updates" #52's macOS runner the sleep resolved after the first tick (count 2). It and calls onUnhealthy when check fails now use Jest fake timers.
• Docs. CONFIG, ARCHITECTURE, DEBUGGING_GUIDE, RELEASING and CHANGELOG [Unreleased] describe the new behaviour instead of the limitations.

Scope

• Area(s): GPU detection, LlamaService backend selection / embedding worker, Windows packaging, Chromium GPU switches, tests, docs
• Risk Level: low to medium (packaging pattern and Linux GPU flags are only exercised by packaged builds)
• Breaking Changes: none

Type of Change

• Bug fix
• Enhancement
• New feature
• Refactor
• Documentation update
• Breaking change

Test Plan

Automated

• npm run format:check
• npm run lint
• npm test (as part of npm run ci on this branch: 774 suites, 11,218 passed, 26 skipped, coverage thresholds met; audit:production 0 vulnerabilities; build OK)
• Additional tests added/updated when behavior changed: driver version parsing and query (GPUMonitor.test.js), read-only record and worker data (llamaBackendCache, llamaBackendSelector, workerPools.threadConfig), per-arch packaging (electron-builder-config, verifyPackagedArtifacts), per-platform raster switches (gpuConfig), fake-timer health checks (healthCheckUtils, 15 consecutive passes).

The affected suites also pass with the starting platform faked to darwin and win32 (14 suites / 420 tests, plus healthCheckUtils/gpuConfig/GPUMonitor after the rebase), so the macOS and Windows runners should not hit platform-only failures.

Manual QA

• Manual checklist completed (see docs/TESTING.md)
• Not applicable (explain below)

Manual QA notes:

• The ${arch} exclusion and the Linux raster switches are only exercised by packaged builds; verify-packaged-artifacts.js now checks the former on every Windows release build. The SW-40 packaged smoke in docs/RELEASING.md still applies before the next release.

Checklist

• I scoped this PR to one logical change
• I self-reviewed code and naming for clarity
• I updated docs/config references where needed
• I called out follow-up work or known limitations

Not done here: macOS and Linux builds still carry better-sqlite3 prebuilds for other platforms (~13 MB each). The same ${arch}-style pattern could trim them, but it needs a packaged mac/Linux build to verify.

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