Merge PR114 dictation foundation for approved provider-row finishing

Preserve original contributor commit 3bb28e5f29. Resolve only the settings-dialog conflict by retaining current General/update behavior: the donor General-only language placement is explicitly superseded by the human-approved row BELOW the full-width Deepgram key. The assigned implementation worker will implement that placement and approved shared dropdown finishing. Foundation only, not a checked candidate.

src/server/settings-body.ts

@@ -19,12 +19,14 @@ import type {
 	BackgroundModelRole,
 	CompactionSettings,
 	GeneralSettings,
+	DictationSettings,
 	GraphSettings,
 	ModelsSettings,
 	RoleModelOverride,
 } from "../core/settings.ts";
 import { BACKGROUND_MODEL_ROLES, COMPACTION_THRESHOLD_FLOOR, EXTRACTION_CHUNK_TOKENS_FLOOR, MODEL_SLOTS } from "../core/settings.ts";
 import { WRITABLE_TOOL_KEYS } from "../core/pending.ts";
+import { isDictationLanguage } from "../core/dictation.ts";
 
 /** Parsed-or-rejected — `ok: false` carries the 400's error message. */
 export type SettingsBodyResult<T> =
@@ -375,6 +377,15 @@ export function parseCompactionSettingsBody(body: unknown): SettingsBodyResult<C
 	return { ok: true, settings };
 }
 
+/** dictation: { language?: one of Nova-3's supported language codes } */
+export function parseDictationSettingsBody(body: unknown): SettingsBodyResult<DictationSettings> {
+	const raw = asRecord(body);
+	if (!raw) return { ok: false, error: "Invalid JSON body" };
+	if (raw.language === undefined) return { ok: true, settings: {} };
+	if (!isDictationLanguage(raw.language)) return { ok: false, error: "Unsupported dictation language" };
+	return { ok: true, settings: { language: raw.language } };
+}
+
 /** The section→parser map for PUT /api/settings/[section] (the route also
  *  carries the special prompts sub-resource). */
 export const SETTINGS_SECTIONS = {
@@ -385,6 +396,7 @@ export const SETTINGS_SECTIONS = {
 	graph: parseGraphSettingsBody,
 	compaction: parseCompactionSettingsBody,
 	models: parseModelsSettingsBody,
+	dictation: parseDictationSettingsBody,
 } as const;
 
 export type SettingsSectionName = keyof typeof SETTINGS_SECTIONS;