WatchedItem detail — bulk 'Add Watches for new sub_aspects' action

[gregoryfoster]

Context

Spun off from #161. Under the InfoItem-first model (#160), Archiver can add new sub_aspect bindings to an InfoItem over time. The WatchedItem detail page (introduced in #161) surfaces these as "N new sub_aspects available since last_reviewed_at" and provides a one-click Mark reviewed action.

The design (Section 5.3 of docs/plans/2026-05-15-watched-item-infoitem-first-design.md) also calls for a bulk "Add Watches for these" action that creates Watches against all new sub_aspect bindings in one operation and stamps last_reviewed_at in the same transaction.

#161 ships Mark-reviewed only; this issue tracks the bulk-add follow-up.

Scope

• Detail-page UI: per-binding checkboxes + "Add Watches for selected" button (and/or "Add Watches for all new").
• Server-side handler: bulk-creates Watch rows under the WatchedItem with sensible defaults (operator-overridable post-create on the standard Watch edit form), stamps last_reviewed_at = now() in the same transaction.
• Audit-log entries per created Watch.

Acceptance

• Operator can select N new sub_aspect bindings and create N Watches in one action.
• last_reviewed_at stamps atomically with the inserts (single transaction).
• New Watches inherit defaults from the parent WatchedItem via the existing live-inheritance chain — no per-row defaults stored at create time.

Related

• WatchedItem CRUD UI — edit shared defaults from the dashboard #161 — WatchedItem CRUD UI (parent issue; ships the Mark-reviewed half).
• InfoItem-first Watch model: WatchedItem, Watch reshape, two-step picker #160 — InfoItem-first Watch reshape (design context).

[gregoryfoster]

Unblocked by #161 — the WatchedItem detail page now ships with the Mark-reviewed half of the sub_aspect review flow. This issue tracks the bulk-add half.