Merge gitea/main into the Motion branch

Motion was written against a base five commits behind main, so the
integration is the interesting part of this commit:

- The migration is renumbered 0014 -> 0015. Main shipped
  0014_piggy_conversations, and two migrations sharing an index is a
  journal that applies one of them.
- The seed-idempotency gate keeps main's all-tables diff rather than the
  motion_templates counter this branch added; the general check subsumes
  the specific one.
- Nav gains a Motion group alongside main's new Workspace group, and
  Piggy keeps the mark main gave it.
- Stat keeps main's container-scaled figure, which already carries the
  min-w-0 this branch added for the same reason.
- Piggy's page labels keep main's refusal wording for the four pages with
  no tool of their own, and gain the three Motion routes.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/motion.md

@@ -98,7 +98,7 @@ title: one 200 and three 409s.
 
 Those two constraints form an FK cycle —
 `motion_templates.origin_artifact_id ↔ engagement_artifacts.template_id` — which
-is why migration `0014_motion.sql` is hand-written and adds one of the two
+is why migration `0015_motion.sql` is hand-written and adds one of the two
 constraints in a separate `ALTER TABLE` after both tables exist. Drizzle will
 not order that for you.