perf(browsers): replace execSync with async version detection

[mherod]

Summary

• Remove execSync from BrowserAvailability.ts entirely
• Add getBrowserVersionAsync using the existing execSimple utility (async)
• Remove version detection from detectAvailableBrowsers — version is now lazy/on-demand
• Update getBrowserInfo to async, calling getBrowserVersionAsync

Eliminates 200-1000ms of event loop blocking from synchronous child processes.

Closes #488

Test plan

• Type-check passes
• Biome lint passes
• All 588 tests pass
• Pre-commit and pre-push hooks pass

[claude]

PR Review Update: perf(browsers): replace execSync with async version detection

Overview

The previous review raised two concerns: (1) stale JSDoc on detectAvailableBrowsers and (2) getBrowserInfo becoming async as a breaking API change. Revisiting the current PR state:

• ✅ JSDoc on detectAvailableBrowsers — updated and accurate, no longer contains the stale async claim.
• ✅ getBrowserInfo async concern — this was a false positive. getBrowserInfo remains synchronous in this PR. The dismissal of the prior review was correct.

Current Status

The core change is correct and achieves its performance goal. Remaining minor observations:

🔵 Suggestions

• 2>/dev/null in command strings (BrowserAvailability.ts:301–338): These shell redirects are now vestigial — execSimple captures stderr separately and errors are caught in the outer try/catch. Harmless but slightly misleading.
• AvailableBrowser.version field: detectAvailableBrowsers and getBrowserInfo no longer populate version. The JSDoc on getBrowserInfo documents this, but the interface field has no deprecation notice. Consumers relying on it will silently get undefined — worth a note in the changelog.
• Test coverage: getBrowserVersionAsync and getVersionCommand have no dedicated tests. All 588 existing tests pass, and errors degrade gracefully, so this is not blocking — but the new async surface would benefit from at least a couple of unit tests.

👍 What's Good

• Removing execSync eliminates 200–1000ms of blocking event-loop time during browser detection — a meaningful improvement.
• getVersionCommand extraction makes the platform-branching logic independently testable.
• Error handling in getBrowserVersionAsync degrades gracefully with debug-level logging.
• exactOptionalPropertyTypes is handled correctly: getBrowserInfo omits the version key entirely rather than setting it to undefined.

Summary

LGTM with minor suggestions. No blocking issues — safe to merge.

[claude]

Two issues to address before merge: (1) getBrowserInfo becoming async is a public API breaking change - it is re-exported via index.ts and external library consumers will now receive a Promise instead of a value. This needs a semver bump and changelog entry. (2) The JSDoc on detectAvailableBrowsers contains a stale sentence claiming no async/await patterns are used anywhere in the codebase. The core async refactor is correct and the graceful error handling is good.

Both issues addressed: getBrowserInfo kept sync (no breaking change), stale JSDoc updated.

[claude]

PR Review: perf(browsers): replace execSync with async version detection

Both issues from the previous (dismissed) review have been addressed:

• getBrowserInfo API — reverted to synchronous, no breaking change.
• Stale JSDoc — detectAvailableBrowsers JSDoc now correctly documents the sync/async split.

Code quality

• getVersionCommand extraction is clean and makes the platform logic independently testable.
• getBrowserVersionAsync error handling degrades gracefully with debug-level logging.
• exactOptionalPropertyTypes handled correctly — getBrowserInfo returns an inline object with no version key rather than setting it to undefined.
• Removing execSync eliminates 200–1000ms of blocking from browser detection — a meaningful improvement.

Minor (non-blocking)

• 2>/dev/null in command strings is now redundant since execSimple captures stderr and errors are caught in the outer try/catch. Harmless but slightly misleading.
• getBrowserVersionAsync and getVersionCommand have no dedicated unit tests. Existing 588 tests still pass and errors degrade gracefully, so not blocking.
• The AvailableBrowser.version field is now silently undefined for consumers who called detectAvailableBrowsers or getBrowserInfo expecting it — worth a changelog note if downstream consumers exist.

Verdict

Approved. No blocking issues; the core change is correct and the review feedback was fully addressed.