fix(pdf): render the pdf dispatch card (live browser-smoke gap)

The browser e2e check on the live dispatch session found the tool-pdf
part rendered NO card: the artifact renderer registry had no pdf entry
(the doc comment literally says "add your renderer here"), and the typed
TeacherUITools union + the chat.tsx job-part enumerations (poll cadence,
dispatch nudge, settle-sync) all missed the new tool kind.

- PdfJobCard in job-card.tsx: the research JobCard idiom, kind pdf —
  registered in artifacts/index.ts.
- ui-message.ts: pdf entry in TeacherUITools (fire-and-forget ack output).
- chat.tsx: two mechanical "tool-pdf" additions to the research/demo/visual
  enumerations — UI-stream file, flagged for review at merge (same
  treatment as the activity-dock type-forced entries).
- demos.test.tsx: live/settled dispatch-card renders + registry pin.

src/core/ui-message.ts

@@ -2,6 +2,7 @@ import type { UIMessage } from "ai";
 import type {
 	DemoToolInput,
 	GraphContextData,
+	PdfToolInput,
 	PlanVerdictData,
 	PlanBlockData,
 	ProbeDoneInput,
@@ -34,6 +35,9 @@ export type TeacherUITools = {
 	research: { input: ResearchToolInput; output: string };
 	demo: { input: DemoToolInput; output: string };
 	visual: { input: VisualToolInput; output: string };
+	/** The pdf dispatch tool (sources v0): fire-and-forget ack output like
+	 *  research — the brief arrives later as a steer message. */
+	pdf: { input: PdfToolInput; output: string };
 };
 
 export type TeacherUIDataParts = {