wave 2 (platform stream): settings storage & plumbing foundation (P2)

- src/core/settings.ts: versioned DELTA record schema + sanitizer (unknown keys preserved)
  — general/chat/agent{models,tools,prompts}/appearance/graph sections
- src/core/settings-resolution.ts: pure resolveSettings (factory defaults → user delta),
  extraction/graph-context channel predicates
- src/store/settings.ts + prompt-overrides.ts: SettingsStore/PromptOverrideStore adapters
  wired through stores.ts (effectiveSettings() fresh per call); lazy migration of
  default-settings.json into record.chat
- app/api/settings/** routes (record, section bodies, prompt overrides per segment)
- chat-handler: graph gates at trigger call-sites + toolToggles injection seam
- config.ts: SETTINGS_FILE + PROMPTS_OVERRIDE_DIR paths

587/587 tests; typecheck/lint/build clean

src/server/stores.ts

@@ -6,14 +6,42 @@
  * file (and the adapter implementations in src/store/).
  */
 
+import { MODELS } from "../../config.ts";
 import { chatStore } from "../store/chats.ts";
 import { graphStore } from "../store/graph.ts";
 import { jobStore } from "../store/jobs.ts";
+import { settingsStore } from "../store/settings.ts";
+import { resolveSettings, type EffectiveSettings, type ModelRoleSpecs } from "../core/settings-resolution.ts";
 /** The wired adapters. Satisfies core/graph.ts's GraphDeps structurally. */
 export const stores = {
 	chatStore,
 	graphStore,
 	jobStore,
+	settingsStore,
 };
 
 export type Stores = typeof stores;
+
+/** config.ts's MODELS narrowed to the background roles — the compiled
+ *  factory layer the resolution reads. core stays pure (it takes this as a
+ *  parameter, never imports config at runtime); the prober/teacher pins
+ *  are chat-settings-controlled and deliberately absent here. Tests pin
+ *  that the role set matches core's BACKGROUND_MODEL_ROLES. */
+const BACKGROUND_MODEL_PINS: ModelRoleSpecs = {
+	researcher: MODELS.researcher,
+	demoBuilder: MODELS.demoBuilder,
+	visualMaker: MODELS.visualMaker,
+	extractor: MODELS.extractor,
+	auditor: MODELS.auditor,
+	labeler: MODELS.labeler,
+};
+
+/**
+ * The resolved view of the settings record (core/settings-resolution.ts):
+ * every knob concrete, record overrides over config.ts factory pins. Read
+ * fresh on every call — the record is a small file and turns are rare, so
+ * no caching layer (stale toggles after a settings PUT would be worse).
+ */
+export function effectiveSettings(): EffectiveSettings {
+	return resolveSettings(settingsStore.readSettings(), BACKGROUND_MODEL_PINS);
+}