feat(run,notifications,profiles): stop sending prompts nobody typed, and fix notification + profile delivery

Run console:
- Picking a pipeline no longer pre-writes anything into the prompt box
  (`promptPrefill` in `LaneConsolePane.tsx` is gone — it wrote the driving
  slash command on a claude lane and a stage checklist on a codex one).
  Whatever sits in that box is sent as a real prompt the moment the run
  starts, so the box is the user's alone now.
- Resuming a session sends NO prompt at all (`handleStart` in `RunSetup.tsx`):
  the resumed session carries its own transcript, and leftover text in the box
  fired an extra turn into it.

Notifications:
- `client/src/lib/notify.ts` is now the ONE sender, used by both
  `useNotifications` and Settings' test button, and it reports where the
  notification landed: `POST /api/push/send` answering `{native:false,pushed:0}`
  means it went NOWHERE, so the client falls back to a local notification
  instead of counting the 200 as delivered.
- A notification carries the lane that raised it (`/workspace?lane=<id>`), and
  Workspace selects that lane on arrival.

Profiles:
- `server/lib/cc-profiles.js` reads and writes the macOS login Keychain item
  `Claude Code-credentials`, where the `claude` CLI actually keeps
  `claudeAiOauth` on darwin — a switch used to rewrite a file nothing reads.
  The file stays the fallback, is kept in step only when it already exists, and
  `AGENTHUB_CC_KEYCHAIN=0` pins it (tests set it).

Tests: npm run test:server (1820 pass), client vitest (553 pass).

server/__tests__/cc-profiles.test.js

@@ -11,6 +11,9 @@ const fs = require("node:fs");
 
 const SUITE_ROOT = fs.mkdtempSync(path.join(os.tmpdir(), "agenthub-cc-profiles-"));
 process.env.CLAUDE_HOME = path.join(SUITE_ROOT, ".claude");
+// File-backed by default, so running this suite on a Mac never reads or rewrites
+// the developer's real login Keychain. The Keychain path has its own test below.
+process.env.AGENTHUB_CC_KEYCHAIN = "0";
 
 const { describe, it, beforeEach, after } = require("node:test");
 const assert = require("node:assert/strict");
@@ -325,6 +328,56 @@ describe("cc-profiles", () => {
     );
   });
 
+  it("switches the account in the macOS Keychain, where the CLI actually reads it", () => {
+    const cp = require("node:child_process");
+    const realExec = cp.execFileSync;
+    const realPlatform = process.platform;
+    Object.defineProperty(process, "platform", { value: "darwin", configurable: true });
+    process.env.AGENTHUB_CC_KEYCHAIN = "1";
+    // A fake `security` binary backed by one string — the keychain item.
+    let item = null;
+    cp.execFileSync = (_bin, args) => {
+      if (args[0] === "find-generic-password") {
+        if (item === null) throw new Error("SecKeychainSearchCopyNext: not found");
+        return item;
+      }
+      if (args[0] === "add-generic-password") {
+        item = args[args.indexOf("-w") + 1];
+        return "";
+      }
+      throw new Error(`unexpected security verb ${args[0]}`);
+    };
+    try {
+      // Logged in as A, Keychain-only: no `.credentials.json` exists at all.
+      login("uuid-a", "a@example.com");
+      fs.rmSync(CREDS, { force: true });
+      item = JSON.stringify({
+        claudeAiOauth: { accessToken: "at-uuid-a", refreshToken: "rt-uuid-a" },
+      });
+      profiles.saveProfile("work");
+
+      login("uuid-b", "b@example.com");
+      fs.rmSync(CREDS, { force: true });
+      item = JSON.stringify({
+        claudeAiOauth: { accessToken: "at-uuid-b", refreshToken: "rt-uuid-b" },
+      });
+      profiles.saveProfile("personal");
+      assert.equal(profiles.listProfiles().items.find((p) => p.active).name, "personal");
+
+      const result = profiles.activateProfile("work");
+      assert.equal(JSON.parse(item).claudeAiOauth.accessToken, "at-uuid-a");
+      assert.ok(
+        result.written.some((w) => w.includes("Keychain")),
+        "the switch must report the Keychain as written"
+      );
+      assert.equal(fs.existsSync(CREDS), false, "no .credentials.json is invented on macOS");
+    } finally {
+      cp.execFileSync = realExec;
+      Object.defineProperty(process, "platform", { value: realPlatform, configurable: true });
+      process.env.AGENTHUB_CC_KEYCHAIN = "0";
+    }
+  });
+
   it("reports a corrupt live credentials file rather than guessing", () => {
     fs.mkdirSync(HOME, { recursive: true });
     fs.writeFileSync(CREDS, "{nope");