fix(browse): stop the headed daemon crash-loop + silent headless downgrade (#1781)

A headed session against a beacon-heavy page (analytics/extension load) could tip
the single-threaded daemon into a self-inflicted crash-loop: a brief HTTP stall
was read as a crash, the restart didn't clear the dead Chromium's SingletonLock,
the relaunch failed, and the session silently came back headless. Four fixes:

1. Busy-vs-dead (sendCommand): on a connection error, if the process is alive give
   /health a bounded probe (3x/250ms) and just retry the command — never kill+restart
   a live-but-busy server. A 30s timeout now reports 'busy, not restarting' when the
   process is alive instead of exiting into a kill cycle.
2. Profile-lock cleanup on (re)start: startServer reaps the orphaned Chromium holding
   the SingletonLock and clears Singleton{Lock,Socket,Cookie} before relaunch, so the
   auto-restart path gets the same clean profile the manual connect preamble did.
3. Headed persistence: the restart env reapplies BROWSE_HEADED from this invocation OR
   the persisted server state (mode==='headed'), so a restart from a plain command
   never downgrades a headed window to invisible headless. Extracted to buildRestartEnv.
4. Force-clean disconnect reaps the Chromium child tree (via the SingletonLock PID) so
   the next connect starts clean instead of fighting an orphan.

Plus macOS window surfacing: connect + focus raise 'Google Chrome for Testing' to the
active Space (best-effort osascript) with a Mission Control hint — the first thing
users read as 'I can't see the browser'.

Shared lock helpers (chromiumProfileDir / cleanChromiumProfileLocks / killOrphanChromium)
dedupe the connect, disconnect, and restart paths. browse/test/restart-env.test.ts pins
the headed-persistence decision; the full crash-loop repro is an E2E (periodic).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

browse/test/restart-env.test.ts

@@ -0,0 +1,39 @@
+import { describe, test, expect } from "bun:test";
+import { buildRestartEnv } from "../src/cli";
+
+// #1781: an auto-restart triggered by a plain command (no --headed flag) must
+// NOT silently downgrade a headed session to headless. buildRestartEnv reapplies
+// headed/proxy/configHash from this invocation OR the persisted server state.
+describe("buildRestartEnv (#1781 headed persistence)", () => {
+  const headedState = { pid: 1, port: 9, token: "t", startedAt: "", serverPath: "", mode: "headed" as const };
+  const launchedState = { pid: 1, port: 9, token: "t", startedAt: "", serverPath: "", mode: "launched" as const };
+
+  test("headed flag on this invocation → BROWSE_HEADED=1", () => {
+    expect(buildRestartEnv({ headed: true } as any, null).BROWSE_HEADED).toBe("1");
+  });
+
+  test("plain command + persisted headed state → still BROWSE_HEADED=1 (the regression)", () => {
+    const env = buildRestartEnv({} as any, headedState as any);
+    expect(env.BROWSE_HEADED).toBe("1");
+  });
+
+  test("plain command + headless state → no BROWSE_HEADED (no spurious headed)", () => {
+    const env = buildRestartEnv({} as any, launchedState as any);
+    expect(env.BROWSE_HEADED).toBeUndefined();
+  });
+
+  test("nothing set → empty env", () => {
+    expect(buildRestartEnv(null, null)).toEqual({});
+  });
+
+  test("proxy + configHash reapplied from flags", () => {
+    const env = buildRestartEnv({ proxyUrl: "socks5://x", configHash: "abc" } as any, null);
+    expect(env.BROWSE_PROXY_URL).toBe("socks5://x");
+    expect(env.BROWSE_CONFIG_HASH).toBe("abc");
+  });
+
+  test("configHash falls back to persisted state", () => {
+    const env = buildRestartEnv({} as any, { ...launchedState, configHash: "fromstate" } as any);
+    expect(env.BROWSE_CONFIG_HASH).toBe("fromstate");
+  });
+});