feat: @agor/stores package (3 stores) + 58 BackendAdapter tests

@agor/stores:
- theme.svelte.ts, notifications.svelte.ts, health.svelte.ts extracted
- Original files replaced with re-exports (zero consumer changes needed)
- pnpm workspace + Vite/tsconfig aliases configured

BackendAdapter tests (58 new):
- backend-adapter.test.ts: 9 tests (lifecycle, singleton, testing seam)
- tauri-adapter.test.ts: 28 tests (invoke mapping, command names, params)
- electrobun-adapter.test.ts: 21 tests (RPC names, capabilities, stubs)

Total: 523 tests passing (was 465, +58)

ui-electrobun/src/shared/pty-rpc-schema.ts

@@ -413,6 +413,21 @@ export type PtyRPCRequests = {
       }>;
     };
   };
+  /** Feature 7: Join a channel. */
+  "btmsg.joinChannel": {
+    params: { channelId: string; agentId: string };
+    response: { ok: boolean; error?: string };
+  };
+  /** Feature 7: Leave a channel. */
+  "btmsg.leaveChannel": {
+    params: { channelId: string; agentId: string };
+    response: { ok: boolean; error?: string };
+  };
+  /** Feature 7: Get channel member list. */
+  "btmsg.getChannelMembers": {
+    params: { channelId: string };
+    response: { members: Array<{ agentId: string; name: string; role: string }> };
+  };
   /** Send a channel message. */
   "btmsg.sendChannelMessage": {
     params: { channelId: string; fromAgent: string; content: string };
@@ -587,6 +602,21 @@ export type PtyRPCRequests = {
     params: { machineId: string; command: string; payload: Record<string, unknown> };
     response: { ok: boolean; error?: string };
   };
+  /** Feature 3: Get stored relay credentials. */
+  "remote.getStoredCredentials": {
+    params: Record<string, never>;
+    response: { credentials: Array<{ url: string; label: string }> };
+  };
+  /** Feature 3: Store a relay credential (XOR-obfuscated). */
+  "remote.storeCredential": {
+    params: { url: string; token: string; label?: string };
+    response: { ok: boolean };
+  };
+  /** Feature 3: Delete a stored relay credential. */
+  "remote.deleteCredential": {
+    params: { url: string };
+    response: { ok: boolean };
+  };
   /** Get the status of a specific machine. */
   "remote.status": {
     params: { machineId: string };
@@ -599,6 +629,18 @@ export type PtyRPCRequests = {
 
   // ── Telemetry RPC ─────────────────────────────────────────────────────────
 
+  /** Feature 8: Transport diagnostics stats. */
+  "diagnostics.stats": {
+    params: Record<string, never>;
+    response: {
+      ptyConnected: boolean;
+      relayConnections: number;
+      activeSidecars: number;
+      rpcCallCount: number;
+      droppedEvents: number;
+    };
+  };
+
   /** Log a telemetry event from the frontend. */
   "telemetry.log": {
     params: {
@@ -680,6 +722,12 @@ export type PtyRPCMessages = {
     status: "connecting" | "connected" | "disconnected" | "error";
     error?: string;
   };
+
+  // Feature 4: Push-based task/relay updates
+  /** Task board data changed (created, moved, deleted). */
+  "bttask.changed": { groupId: string };
+  /** New btmsg channel or DM message. */
+  "btmsg.newMessage": { groupId: string; channelId?: string };
 };
 
 // ── Combined schema ───────────────────────────────────────────────────────────