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/lib/cc-profiles.js

@@ -5,7 +5,8 @@
  * anything else in the Claude home.
  *
  * A profile is exactly the two identity artifacts and nothing more:
- *   - `claudeAiOauth` out of `<CLAUDE_HOME>/.credentials.json`
+ *   - `claudeAiOauth` out of `<CLAUDE_HOME>/.credentials.json` — or, on macOS,
+ *     out of the login Keychain item the CLI actually reads there
  *   - `oauthAccount` + `userID` out of the `.claude.json` config file(s)
  * Skills, subagents, commands, memory, plugins, marketplaces, MCP servers,
  * settings and session history all live elsewhere under CLAUDE_HOME and are
@@ -23,10 +24,59 @@
  */
 
 const fs = require("node:fs");
+const os = require("node:os");
 const path = require("node:path");
+const cp = require("node:child_process");
 
 const { getClaudeHome } = require("./claude-home");
 
+/**
+ * On macOS the `claude` CLI keeps `claudeAiOauth` in the login Keychain, NOT in
+ * `<CLAUDE_HOME>/.credentials.json` — a file there is absent or a stale leftover
+ * from an older build. Reading/writing only the file on a Mac is why a switch
+ * reported success while the CLI kept running as the previous account.
+ */
+const KEYCHAIN_SERVICE = "Claude Code-credentials";
+const KEYCHAIN_LABEL = `macOS Keychain (${KEYCHAIN_SERVICE})`;
+
+/** Off with AGENTHUB_CC_KEYCHAIN=0 — tests, and anyone pinning the file. */
+function keychainEnabled() {
+  return process.platform === "darwin" && process.env.AGENTHUB_CC_KEYCHAIN !== "0";
+}
+
+function keychainArgs(verb) {
+  return [verb, "-s", KEYCHAIN_SERVICE, "-a", os.userInfo().username];
+}
+
+/** The keychain item's JSON, or null when there is none / it is unreadable. */
+function readKeychain() {
+  try {
+    const out = cp.execFileSync(
+      "/usr/bin/security",
+      [...keychainArgs("find-generic-password"), "-w"],
+      {
+        encoding: "utf8",
+        stdio: ["ignore", "pipe", "ignore"],
+      }
+    );
+    const parsed = JSON.parse(out.trim());
+    return parsed && typeof parsed === "object" ? parsed : null;
+  } catch {
+    return null;
+  }
+}
+
+function writeKeychain(value) {
+  // ponytail: the secret rides in argv (`security` has no stdin mode), so it is
+  // briefly visible in `ps` on a shared machine. Upgrade path is a native
+  // keychain binding if that ever matters.
+  cp.execFileSync(
+    "/usr/bin/security",
+    [...keychainArgs("add-generic-password"), "-U", "-w", JSON.stringify(value)],
+    { stdio: "ignore" }
+  );
+}
+
 /**
  * A profile's `name` is its filename, so the charset is deliberately narrow.
  * It is an internal identifier: what the user reads and edits is `label`, which
@@ -84,9 +134,38 @@ function writeJson(file, value) {
   fs.renameSync(tmp, file);
 }
 
+/**
+ * The live credentials blob and where it came from. The Keychain wins on macOS
+ * when it holds an item; everything else (and a Mac whose CLI still uses the
+ * file) falls back to `.credentials.json`.
+ */
+function readCredentials() {
+  if (keychainEnabled()) {
+    const kc = readKeychain();
+    if (kc) return { creds: kc, keychain: true };
+  }
+  return { creds: readJson(credentialsPath()), keychain: false };
+}
+
+/** Write credentials back to the store they were read from. Returns what was written. */
+function writeCredentials(creds, keychain) {
+  if (!keychain) {
+    writeJson(credentialsPath(), creds);
+    return [credentialsPath()];
+  }
+  writeKeychain(creds);
+  // A stale file beside the Keychain would still name the old account; keep it
+  // in step when it exists, never create one.
+  if (fs.existsSync(credentialsPath())) {
+    writeJson(credentialsPath(), creds);
+    return [KEYCHAIN_LABEL, credentialsPath()];
+  }
+  return [KEYCHAIN_LABEL];
+}
+
 /** The account identity currently on disk. `oauth`/`account` may be null. */
 function readActiveAuth() {
-  const creds = readJson(credentialsPath());
+  const { creds, keychain } = readCredentials();
   let account = null;
   let userID = null;
   for (const file of configPaths()) {
@@ -97,7 +176,7 @@ function readActiveAuth() {
       break;
     }
   }
-  return { oauth: (creds && creds.claudeAiOauth) || null, account, userID };
+  return { oauth: (creds && creds.claudeAiOauth) || null, account, userID, keychain };
 }
 
 /** Token-free description of an account, safe to send to the browser. */
@@ -344,12 +423,12 @@ function activateProfile(name) {
   }
 
   const written = [];
-  const creds = readJson(credentialsPath()) || {};
+  const { creds: live, keychain } = readCredentials();
+  const creds = live || {};
   // Only the Claude account slot moves; `mcpOAuth` holds this machine's MCP
   // server tokens, which are not part of the account identity.
   creds.claudeAiOauth = target.credentials;
-  writeJson(credentialsPath(), creds);
-  written.push(credentialsPath());
+  written.push(...writeCredentials(creds, keychain));
 
   for (const file of configPaths()) {
     const cfg = readJson(file);