feat(core): add FeedController orchestration layer

Adds orchestration for feed reconciliation with context-driven updates:

- FeedController: holds context, debounces updates, reconciles sources
- ContextBridge: bridges context providers to controller
- ContextProvider: reactive + on-demand context value interface
- Branded ContextKey<T> for type-safe context keys

Moves source files to src/ directory and consolidates tests into
integration test.

Co-authored-by: Ona <no-reply@ona.com>

packages/aris-core/src/context-bridge.ts

@@ -0,0 +1,79 @@
+import type { Context } from "./context"
+import type { ContextProvider } from "./context-provider"
+
+interface ContextUpdatable {
+	pushContextUpdate(update: Partial<Context>): void
+}
+
+/**
+ * Bridges context providers to a feed controller.
+ *
+ * Subscribes to provider updates and forwards them to the controller.
+ * Supports manual refresh to gather current values from all providers.
+ *
+ * @example
+ * ```ts
+ * const controller = new FeedController()
+ *   .addDataSource(new WeatherDataSource())
+ *   .addDataSource(new TflDataSource())
+ *
+ * const bridge = new ContextBridge(controller)
+ *   .addProvider(new LocationProvider())
+ *   .addProvider(new MusicProvider())
+ *
+ * // Manual refresh gathers from all providers
+ * await bridge.refresh()
+ *
+ * // Cleanup
+ * bridge.stop()
+ * controller.stop()
+ * ```
+ */
+export class ContextBridge {
+	private controller: ContextUpdatable
+	private providers = new Map<string, ContextProvider>()
+	private cleanups: Array<() => void> = []
+
+	constructor(controller: ContextUpdatable) {
+		this.controller = controller
+	}
+
+	/**
+	 * Registers a context provider. Immediately subscribes to updates.
+	 */
+	addProvider<T>(provider: ContextProvider<T>): this {
+		this.providers.set(provider.key, provider as ContextProvider)
+
+		const cleanup = provider.onUpdate((value) => {
+			this.controller.pushContextUpdate({ [provider.key]: value })
+		})
+		this.cleanups.push(cleanup)
+
+		return this
+	}
+
+	/**
+	 * Gathers current values from all providers and pushes to controller.
+	 * Use for manual refresh when user pulls to refresh.
+	 */
+	async refresh(): Promise<void> {
+		const updates: Partial<Context> = {}
+
+		const entries = Array.from(this.providers.entries())
+		const values = await Promise.all(entries.map(([_, provider]) => provider.getCurrentValue()))
+
+		entries.forEach(([key], i) => {
+			updates[key] = values[i]
+		})
+
+		this.controller.pushContextUpdate(updates)
+	}
+
+	/**
+	 * Unsubscribes from all providers.
+	 */
+	stop(): void {
+		this.cleanups.forEach((cleanup) => cleanup())
+		this.cleanups = []
+	}
+}