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/artifacts/index.ts

@@ -1,7 +1,7 @@
 import type { ComponentType } from "react";
 import type { ArtifactPartProps } from "@/src/core";
 import { DemoCard } from "@/components/artifacts/demo-card";
-import { JobCard } from "@/components/artifacts/job-card";
+import { JobCard, PdfJobCard } from "@/components/artifacts/job-card";
 import { VisualCard } from "@/components/artifacts/visual-card";
 import { ProbeDoneCard } from "@/components/artifacts/probe-done-card";
 
@@ -19,6 +19,7 @@ import { ProbeDoneCard } from "@/components/artifacts/probe-done-card";
  */
 export const artifactRenderers: Record<string, ComponentType<ArtifactPartProps>> = {
 	research: JobCard,
+	pdf: PdfJobCard, // sources v0 — live smoke 2026-09-19 caught the gap: without this the tool-pdf dispatch part rendered nothing
 	// plan_* parts render nothing inline by design: the phase seam is a
 	// message-level boundary, drawn by PhaseDivider in chat.tsx (the old
 	// part-level plan_init divider retired with it).