Refactor: dedupe status emission, region resolution, config save

[yarikleto]

What

Behavior-preserving cleanup of three small duplication spots, ahead of review.

• monitor.js — merged the two byte-identical baseline branches (first frame / size change) into one `isBaseline` guard; added `emitStatus()` helper that removes 3× repeated `new Date().toLocaleTimeString()` and verbose status objects. Resolution-change rationale preserved in comment.
• main.js — added `resolveRegion(value)` helper replacing the `if (regionResolve) { regionResolve(x); regionResolve = null; }` pattern repeated 3×.
• config.js — collapsed `save()` loop to `store.set(cfg)` (electron-store v8 accepts an object; same per-entry iteration, single atomic write).

Not done

• Skipped rewriting `config.getAll()` to derive keys from defaults — explicit, greppable key list beats indirection.

Verification

• `npm test` — 8/8 pass
• `npm run lint` — clean
• No behavior change.