Local↔remote sync for DB-native detection review (pull/push)

[Chouffe]

Extracted as an orthogonal feature from the DB-native model-assisted detection-review design (docs/specs/2026-07-17-detection-review-db-native-design.md).

Goal

Feed a local pyro-annotator instance from the remote and push reviewed results back, so the DB-native review capability can replace the FiftyOne loop end-to-end. Auto-annotate itself is independent of this (it runs against whatever DB the API points at).

Scope

• Pull: bring seq_annotation_done sequences into the local DB in a reviewable state (detection annotations present). Reuse READ_ONLY_SOURCE to leave the remote untouched.
• Push: DB→remote, mirroring apply_fiftyone_review semantics — clean → annotated; issue frames → needs_manual / bbox_annotation. Support --dry-run.

Open detail

Exact pull mechanism to create local detection annotations: clone + locally set the sequence annotation to annotated (triggering PR #150's server-side auto-create), or a dedicated pull path.

Relation

• Prerequisite for fully retiring FiftyOne (the review-capability spec covers provenance + auto-annotate + review UI; this issue covers getting data in/out).
• May graduate to its own design doc if it grows.