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.

components/chat.tsx

@@ -549,7 +549,14 @@ export function Chat({
 				(n, m) =>
 					n +
 					m.parts.filter(
-						(p) => p.type === "tool-research" || p.type === "tool-demo" || p.type === "tool-visual",
+						// sources v0 — "tool-pdf" added to the job-part enumerations
+						// (mechanical, UI-stream review at merge): poll cadence +
+						// dispatch nudge + settle-sync all key on these parts.
+						(p) =>
+							p.type === "tool-research" ||
+							p.type === "tool-demo" ||
+							p.type === "tool-visual" ||
+							p.type === "tool-pdf",
 					).length,
 				0,
 			),
@@ -576,7 +583,10 @@ export function Chat({
 		for (const m of messages) {
 			for (const p of m.parts) {
 				if (
-					(p.type === "tool-research" || p.type === "tool-demo" || p.type === "tool-visual") &&
+					(p.type === "tool-research" ||
+						p.type === "tool-demo" ||
+						p.type === "tool-visual" ||
+						p.type === "tool-pdf") && // sources v0 — see the poll-cadence enumeration above
 					p.toolCallId &&
 					p.state !== "input-streaming" &&
 					p.state !== "output-error"