W2: async job infra + researcher sub-agent

- src/store/jobs.ts: per-job JSON store in data/jobs (create/get/update/list,
  dedup by toolCallId)
- src/agent/tools/jobs.ts: research tool — client-side (no execute), turn ends
  at the call; input per contracts ResearchToolInput
- src/agent/tools/web.ts: server-side web_search (Google CSE) + web_fetch
  (Readability/Turndown/linkedom, Jina fallback) — errors return as strings,
  never thrown into the agent loop. Deps: @mozilla/readability, linkedom,
  turndown (+@types/turndown dev)
- src/agent/subagents/researcher.ts: isolated ToolLoopAgent (web tools only,
  12-step cap), researcher prompt ported from pi
- src/agent/subagents/runner.ts: spawnPendingJobs hook + runResearchJob —
  fire-and-forget, activity line per tool call, fulfills the part in the
  LATEST chat record (output-available) before flipping job status; failure
  still fulfills the part so the teacher learns the outcome
- src/server/chat-handler.ts: onFinish spawn hook after saveMessages
- app/api/jobs/route.ts: GET ?chatId= polling endpoint
- components/artifacts/job-card.tsx + registry entry: polling activity card
  (2s) → syncFromServer on finish; research-brief card (markdown + sources)
- src/agent/prompts/20-jobs.md: research doctrine for the teacher
- tests/jobs.test.ts: store CRUD, spawn hook via scripted mock teacher,
  runner completion/failure with fake model + stubbed fetch

package.json

@@ -16,6 +16,7 @@
 	},
 	"dependencies": {
 		"@ai-sdk/react": "^4.0.79",
+		"@mozilla/readability": "^0.6.0",
 		"@openrouter/ai-sdk-provider": "^3.0.0",
 		"@radix-ui/react-use-controllable-state": "^1.2.6",
 		"@rive-app/react-webgl2": "^4.32.1",
@@ -31,8 +32,10 @@
 		"cmdk": "^1.1.1",
 		"embla-carousel-react": "^8.6.0",
 		"katex": "^0.16.47",
+		"linkedom": "^0.18.13",
 		"lucide-react": "^1.33.0",
 		"media-chrome": "^4.19.2",
+		"mermaid": "^11.17.0",
 		"motion": "^13.1.1",
 		"nanoid": "^6.0.1",
 		"next": "^16.3.2",
@@ -41,9 +44,11 @@
 		"react": "^19.2.8",
 		"react-dom": "^19.2.8",
 		"react-jsx-parser": "^2.4.1",
+		"remark-breaks": "^4.0.0",
 		"streamdown": "^2.5.0",
 		"tailwind-merge": "^3.6.0",
 		"tokenlens": "^1.3.1",
+		"turndown": "^7.2.4",
 		"use-stick-to-bottom": "^1.1.6",
 		"zod": "^4.4.3"
 	},
@@ -52,6 +57,7 @@
 		"@types/node": "^24.0.0",
 		"@types/react": "^19.2.18",
 		"@types/react-dom": "^19.2.4",
+		"@types/turndown": "^5.0.6",
 		"tailwindcss": "^4.3.3",
 		"tsx": "^4.19.0",
 		"typescript": "^5.6.0"