[codex] Prepare Media Studio assistant release

[gateway]

Summary

This PR prepares the Media Studio assistant and Graph Studio release work for review.

• Adds the dev-flagged Media Assistant stack for graph, preset, recipe, selected-node, character sheet, and storyboard workflows.
• Keeps the assistant hidden unless NEXT_PUBLIC_MEDIA_STUDIO_ASSISTANT_DEBUG=1 is enabled and /api/control/health proves codex_local_ready: true.
• Adds and hardens Graph Studio workflow execution, run history, media selectors, pricing estimates, node layout behavior, context menus, grouped workflows, prompt recipe nodes, and artifact handling.
• Adds Prompt Recipe support for Character Sheet v3, Storyboard v2, and Storyboard Continuation with stricter layout, continuity, dialogue, and handoff behavior.
• Updates Studio and Graph pricing/validation for motion-control video metadata, duration-aware estimates, and model option propagation.
• Surfaces newer KIE models through Studio and Graph Studio, including Kling motion-control flows, Kling 3.0 Turbo image-to-video, Seedance 2.0 Fast, and Seedance 2.0 Mini.
• Consolidates Studio, Settings, and Graph Studio UI/style patterns and removes selected legacy compatibility paths after verification.
• Improves generated/imported media library selector behavior and extends the shared media selector approach.

Database / migrations

This branch includes schema migrations through version 29:

• v5-v7: Graph Studio workflows, templates, runs, run metrics, artifacts, and artifact lineage indexes.
• v8-v16: Prompt Recipes, validation warnings, drafting config, recipe seed refreshes, external LLM usage, rollout cleanup, and drafting enabled state.
• v17-v19: Media Assistant sessions, messages, attachments, plans, validated workflow snapshots, and per-turn usage diagnostics.
• v20-v23: Media Preset categories, category backfills/corrections, and media asset dimension metadata.
• v24-v29: Storyboard Continuation and Storyboard recipe seed refreshes for simplified fields, safer action language, continuity ledger, dialogue placeholders, and full-dialogue behavior.

Before merging, run migrations against a backed-up local or staging DB and verify seeded built-in recipes refresh on an existing DB.

Release flags and content notes

• Keep NEXT_PUBLIC_MEDIA_STUDIO_ASSISTANT_DEBUG unset/off outside internal development.
• Even with the flag on, the Graph Studio assistant launcher is hidden unless Codex Local readiness is proven by health check.
• User-importable Media Preset bundles should be exported into content/media-presets/.
• User-importable Prompt Recipe bundles should be exported into content/prompt-recipes/.
• This PR intentionally does not include the internal docs/engineering/, docs/engineering-audit/, or local runtime/output/tmp artifacts.

Verification

• git diff --cached --check
• npm --workspace apps/web test -- graph-assistant-debug.test.ts
• npm --workspace apps/web run typecheck -- --pretty false
• npm --workspace apps/web test -- graph-tabs.test.ts graph-prompt-provider.test.ts graph-node-field.test.tsx creative-assistant-panel.test.tsx graph-left-rail.test.tsx
• ./scripts/with_shared_python.sh -m pytest apps/api/tests/test_graph_studio.py apps/api/tests/test_media_assistant.py apps/api/tests/test_store_seed_data.py -q --maxfail=1 passed with 432 tests.
• Browser check in the in-app browser loaded /graph-studio; health returned codex_local_ready: true, and the Media Assistant launcher was visible without runtime overlay errors.