Surface style-capture failures instead of silent swallow

[hungify]

What to build

captureStyleIssues in packages/playwright/src/to-match-figma.ts:35-47 catches every error during style capture and returns []. A broken selector, a crashed page.$eval, or any other capture failure is currently indistinguishable from "styles match" — no diagnostic is ever surfaced. Fix this so capture failures produce a visible diagnostic/issue instead of silently returning an empty result.

Acceptance criteria

• A selector that fails to resolve (not found, detached, etc.) during style capture produces a distinct, surfaced diagnostic — not an empty issues array
• Existing successful style-capture paths are unaffected (no new false positives on styles that do match)
• Dashboard/CLI output makes a capture failure visually distinguishable from a clean style-check pass
• Unit test covering: selector-not-found, DOM eval throwing, and the existing happy path

Blocked by

None — can start immediately.