Unify real evidence artifacts end to end

[dgyy]

Parent

Part of #22.

What to build

Make one captured evidence bundle pass unchanged through browser capture, validation, assessment, CI artifact transport, and publication, including real screenshot files with verified integrity.

Acceptance criteria

• Browser capture writes actual desktop and mobile screenshot files when the corresponding observation succeeds.
• Evidence records reference existing artifacts and include sufficient integrity metadata to detect missing or substituted files.
• Capture output is consumable by assessment and publication without path rewriting or manual movement.
• CI upload/download layout matches the local contract.
• Tests fail for metadata-only screenshots, missing files, hash mismatches, broken loads, and malformed artifact layouts.
• A valid fixture completes the capture-to-publication contract without human intervention.

Blocked by

None (can start immediately).