[U34] Capture and freshness-check real documentation screenshots

[ZempTime]

PRD: #1
Delivery unit: U34
Campaign: C10
Canonical graph: https://github.com/ZempTime/shortbread/blob/246320c73d81e5afdf0490b43a2b02272f40268b/docs/initiatives/2026-07-shortbread-v1/05_delivery_replan/output/2026-07-20-delivery-plan.md
Common unit contract: https://github.com/ZempTime/shortbread/blob/246320c73d81e5afdf0490b43a2b02272f40268b/docs/initiatives/2026-07-shortbread-v1/05_delivery_replan/output/UNIT-CONTRACT.md

• Acceptance umbrella / blockers: GitHub Ship a public-source tour and repeatable screenshots #15; blocked by U33.
• Outcome: A repeatable browser harness captures current real-app desktop/mobile documentation screenshots with deterministic state, stable filenames, accessible captions/alt text, and a manifest that fails when required images are absent or stale.
• Failure/recovery: Wrong viewport/state, nondeterminism, stale flow, missing accessibility metadata, private data, and manual image drift fail the freshness check.
• Evidence: Screenshot regeneration, manifest/digest/freshness tests, visual/accessibility review, privacy scan, and clean rerun.
• Central surfaces / impact: Generated screenshots are controller-exclusive; harness, manifest, docs image references. No image is accepted from mockups or synthetic rendering outside the app.
• Safe split: Capture harness and final image set may checkpoint separately, but generation/freshness must be one command contract.

Every integration records a factory candidate with evidence or No reusable harvest.