feat(kt-db): bump DefaultGraphTypePlugin to v2 with noop migration (Phase 7 #60)

[charlie83Gs]

Summary

First real exercise of the Phase 7 migration framework end-to-end.
Composition is unchanged from v1 — the only effect of bumping is that
every v1 graph auto-dispatches onto `graph_migration_wf` at worker
boot, the banner briefly shows `read_only_reason='migrating'`, one
audit row lands, and the graph ends at v2.

Intentional operator-visible exercise of the migration path before
a real v3 recipe change ships.

Proves

• Startup auto-dispatch (feat(worker-synthesis): store synthesis errors and add regeneration #58 / PR feat(kt-db): startup auto-dispatch for out-of-date graphs (Phase 7 #58) #269) picks up out-of-date graphs.
• The Hatchet workflow (feat(wiki-frontend): add homepage tabs, synthesis views, and fix definition rendering #57 / PR feat(worker-bottomup): graph_migration_wf Hatchet workflow (Phase 7 #57) #267) commits per-hop.
• The audit table + the read-only banner surface the transition.

What it's NOT

• Not a composition change. Provider ids are identical to v1.
• Not a data migration. Uses `NoopMigration` — the ready-made class
  `plan.md` specifies for version bumps that change composition-as-
  config but require no data work.

Dependencies

Depends on PR #267 (workflow) and PR #269 (auto-dispatch) being merged
for the plugin bump to actually drive a migration round-trip. Merging
this in isolation is safe — the bump just pins `current_version=2` in
the plugin; without the workflow + dispatcher registered, graphs stay
at v1 until those land (then re-register on next boot).

Test plan

• `uv run --project libs/kt-config pytest libs/kt-config/tests/ -x` — 236/236
• `uv run --project libs/kt-db pytest libs/kt-db/tests/integration/ -x` — 230/230
• `uv run --project services/api pytest services/api/tests/integration/ -x` — 131/131
• CI green

🤖 Generated with Claude Code

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