fix: bound legacy ffmpeg frame-extraction calls with a timeout

[Praveen Kumar Mittal (mittalpk)]

Fixes #14.

What's wrong

extractLegacyWindow/extractLegacySingle in electron/frames/extractor.ts run the system ffmpeg binary via execFileAsync(ffmpegPath, [...], { maxBuffer }), with no timeout. If ffmpeg stalls (corrupt input, codec edge case, stuck pipe), the promise never settles and frame extraction — and the describer/analysis pipeline behind it — hangs indefinitely for that session.

Fix

Added a LEGACY_FFMPEG_TIMEOUT_MS (60s) constant and passed it as timeout on both execFileAsync calls. On timeout, Node kills the child and the call rejects, which both call sites already route into their existing catch (log a warning, return an empty/null result) — the same handling as any other ffmpeg failure, so no new error-handling path was needed.

How I tested it

• extractLegacyWindow/extractLegacySingle are private and resolve their ffmpeg binary through a module-level, cached which/where lookup that isn't test-injectable without expanding this fix's scope. Instead, added a test that exercises the same mechanism directly: a genuinely hung child process (node -e "setInterval(...)"), asserting execFileAsync with a timeout kills it and rejects well within the bound rather than hanging.
• npm test: 155/158 pass; 2 failures + 1 cancelled, all confirmed identical on unpatched main with none of this PR's changes — unrelated (a pre-existing debug-bundle.test.ts/archiver typing issue and a flaky microphone-controller test).
• npm run typecheck: pre-existing, unrelated failures in debug-bundle.ts also confirmed identical on main; no new errors from this change.

[adilei]

Thanks for tackling this and for highlighting the unbounded ffmpeg call. We fixed #14 for 0.6.0 in #69 by removing the legacy system-ffmpeg fallback entirely: captured-frame manifests have shipped in every tagged release since v0.1.0, so deleting the unreleased compatibility path also eliminates timeout and partial-output failure modes. Closing this PR as superseded by #69.