Add lightweight experience receipts

[mattheliu]

What changed

• place tiny plugin thumbs on the first Agent reply after a trial
• use the same compact fallback for command, UI, and crash plugins with no reply
• generate a fixed local de-identified Summary before any network request
• let the Agent choose a closed category from public plugin identity and Host state only
• add a local receipt box plus independent confirmation and aggregate follow-up

Privacy impact

The UI anchor reads only the finalized message ID and timestamp. It never reads reply blocks, task text, tool inputs/results, files, logs, or error details. The network schema still rejects free text and unknown fields.

Validation

• pnpm test:all
• DSH 0.1.0-rc.6 pack/install/boot/uninstall E2E
• local browser flow: thumbs → de-identified preview → explicit confirm → receipt
• git diff --check