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/settings-body.ts

@@ -22,6 +22,7 @@ import type {
 	RoleModelOverride,
 } from "../core/settings.ts";
 import { BACKGROUND_MODEL_ROLES } from "../core/settings.ts";
+import { TOGGLEABLE_TOOLS } from "../core/pending.ts";
 
 /** Parsed-or-rejected — `ok: false` carries the 400's error message. */
 export type SettingsBodyResult<T> =
@@ -166,7 +167,20 @@ export function parseAgentSettingsBody(body: unknown): SettingsBodyResult<AgentS
 	}
 	const tools = parseBooleanMap(raw.tools, "tools");
 	if (tools.error) return { ok: false, error: tools.error };
-	if (tools.map) settings.tools = tools.map;
+	if (tools.map) {
+		// Unknown tool keys are rejected at WRITE time (user decision
+		// 2026-09-19): the delta is inert while unread, but once the bridge
+		// honors it a persisted `quiz: false` would genuinely drop the quiz —
+		// and the definitive list is the adjudicated job-tools-only set.
+		// The read-side sanitizer stays lenient for forward-compat.
+		const supported = TOGGLEABLE_TOOLS as readonly string[];
+		for (const key of Object.keys(tools.map)) {
+			if (!supported.includes(key)) {
+				return { ok: false, error: `unknown tool "${key}" (supported: ${supported.join(", ")})` };
+			}
+		}
+		settings.tools = tools.map;
+	}
 	const prompts = parseBooleanMap(raw.prompts, "prompts");
 	if (prompts.error) return { ok: false, error: prompts.error };
 	if (prompts.map) settings.prompts = prompts.map;