feat(tools): the P2 toggle bridge — toolToggles first-class, definitive vocabulary

Reconciliation of the diverged tool-toggles seam (2026-09-19, master's
P2): Platform injected the resolved delta as an ad-hoc intersection on
AgentBuildOptions while the factories' enabled? param sat unread — the
seam was inert on both sides.

- teacher-agent: AgentBuildOptions gains toolToggles?: EnabledTools;
  both constructors thread it to the factories (createTeacherTools /
  createProberTools). An explicitly injected opts.tools registry is
  never filtered — the caller owns it.
- Vocabulary ADJUDICATED with the user (2026-09-19): TOGGLEABLE_TOOLS is
  the definitive list — the job tools only (research/demo/visual/pdf).
  quiz/ask_user_question stay always-on forever (the prober's flow is
  graded-quiz brackets -> probe_done; quiz-off collapses assessment and
  teaching doctrine is built on graded verification — the wedge danger);
  the learner-fs set, plan tools, and probe_done also always-on.
- settings-body (write side): unknown tool keys reject with 400 + the
  supported list, mirroring the prompt-switch validation; the read-side
  sanitizer stays lenient for forward-compat.
- chat-handler: the intersection is gone (field now first-class) and the
  seam comment states the adjudicated vocabulary.

Gates: typecheck, 28 new/updated tests green (tool-toggles-bridge,
question-tools, settings-body), chat-flow + settings suites green.

src/server/chat-handler.ts

@@ -210,13 +210,14 @@ export async function handleChatRequest(
 	// Tests inject a factory: the agent is stateless per turn (docs/
 	// pi-engine-swap.md §2), so each request builds a fresh one off the
 	// transcript — the factory mirrors that seam exactly.
-	// CROSS-STREAM SEAM (agreed 2026-09-19, settings wave): `toolToggles`
+	// CROSS-STREAM SEAM (P2 reconciliation, 2026-09-19): `toolToggles`
 	// rides the build opts as the user-level DELTA map (absent key =
-	// enabled — quiz, ask_user_question, research, demo, visual). The
-	// Teacher stream adds the field to AgentBuildOptions + the filtering in
-	// createTeacherTools / the prober's registry this same wave; until that
-	// merge, the extra property is structurally ignored (a harmless no-op).
-	const agentOpts: AgentBuildOptions & { toolToggles?: Record<string, boolean> } = {
+	// enabled). The definitive toggleable set is TOGGLEABLE_TOOLS — the
+	// sub-agent JOB tools (research/demo/visual/pdf; adjudicated with the
+	// user: quiz/ask/fs/plan/probe_done are always-on). First-class on
+	// AgentBuildOptions; the factories drop anything explicitly false and
+	// the settings write side rejects unknown keys.
+	const agentOpts: AgentBuildOptions = {
 		engine,
 		messages: recordToPiMessages(outgoing),
 		onUsage: collectUsage,