Separate Studio 2 source and canvas and apply size and seed choices

tests/studio2-runner.test.mjs

@@ -1,3 +1,4 @@
+import {queueSeeds} from '../shared/studio2/seed.mjs'
 import test from 'node:test'
 import assert from 'node:assert/strict'
 import {readFileSync,mkdtempSync,mkdirSync,writeFileSync,existsSync} from 'node:fs'
@@ -16,7 +17,7 @@ function fixture(mode='video') {
  const job={status:'running',clientId:'client',library:{}}
  let id=0
  const scope={
-  watchProgress:()=>()=>{},compilePrompt,saveRecord(){},update(r,state){r.state=state;phases.push(state)},acquireSharedGpu:async()=>true,ensureComfyReady:async()=>{},emitJob(){},
+  queueSeeds,watchProgress:()=>()=>{},compilePrompt,saveRecord(){},update(r,state){r.state=state;phases.push(state)},acquireSharedGpu:async()=>true,ensureComfyReady:async()=>{},emitJob(){},
   prepareGraph:async r=>{queued.push({hero:r.request.identityStillId,start:r.request.startClipId,action:r.request.promptSections.action});return {}},queuePrompt:async()=>({prompt_id:`p${++id}`}),
   fetchHistory:async p=>({[p]:{status:{status_str:'success'},outputs:{}}}),comfyFetch:()=>{throw new Error('Unexpected network call')},
   extractVideo:()=>({filename:'video.mp4',subfolder:'preview/studio2/r',type:'output'}),extractEditedImage:()=>({filename:'image.png',subfolder:'preview/studio2/r',type:'output'}),