fix: make navigation no-focus by default

- Change nav open and open-wait to avoid activating newly created tabs unless
  --focus is explicitly requested.
- Send background=true for default opens so older or remote extensions also
  avoid stealing focus even if they ignore the new focus flag.
- Remove the redundant --bg flag from navigation and search CLI commands now
  that no-focus/background behavior is the default.
- Thread focus support through the sync SDK, async SDK, tab helpers, and
  workflow decorators.
- Update README and demo usage to document the new default and --focus opt-in.
- Bump package and extension metadata to 0.12.3.
- Add regression coverage for CLI help, wire payloads, and extension behavior.

tests/test_commands_cli.py

@@ -346,14 +346,43 @@ def test_cli_perf_profile_ultra():
 from browser_cli.commands.navigate import nav_group
 
 def test_cli_nav_open():
-    result = _run(nav_group, ["open", "https://example.com"], {"id": 42, "url": "https://example.com"})
-    assert result.exit_code == 0
-    assert "Opened" in result.output
+    with patch("browser_cli.send_command", return_value={"id": 42, "url": "https://example.com"}) as send_command:
+        result = CliRunner().invoke(nav_group, ["open", "https://example.com"])
 
-def test_cli_nav_open_bg():
-    result = _run(nav_group, ["open", "https://example.com", "--bg"], {"id": 42})
     assert result.exit_code == 0
     assert "Opened" in result.output
+    send_command.assert_called_once_with(
+        "navigate.open",
+        {"url": "https://example.com", "background": True, "focus": False, "window": None, "group": None},
+        profile=None,
+        remote=None,
+        key=None,
+    )
+
+def test_cli_nav_open_has_no_bg_option():
+    result = CliRunner().invoke(nav_group, ["open", "--help"])
+
+    assert result.exit_code == 0
+    assert "--bg" not in result.output
+
+def test_cli_nav_open_wait_has_no_bg_option():
+    result = CliRunner().invoke(nav_group, ["open-wait", "--help"])
+
+    assert result.exit_code == 0
+    assert "--bg" not in result.output
+
+def test_cli_nav_open_focus_is_explicit():
+    with patch("browser_cli.send_command", return_value={"id": 42}) as send_command:
+        result = CliRunner().invoke(nav_group, ["open", "https://example.com", "--focus"])
+
+    assert result.exit_code == 0
+    send_command.assert_called_once_with(
+        "navigate.open",
+        {"url": "https://example.com", "background": False, "focus": True, "window": None, "group": None},
+        profile=None,
+        remote=None,
+        key=None,
+    )
 
 def test_cli_nav_open_with_group():
     result = _run(nav_group, ["open", "https://example.com", "--group", "work"], {"id": 42})
@@ -412,6 +441,18 @@ def test_cli_nav_wait():
     assert result.exit_code == 0
     assert "Ready" in result.output
 
+# ---------------------------------------------------------------------------
+# search commands
+# ---------------------------------------------------------------------------
+
+from browser_cli.commands.search import search_group
+
+def test_cli_search_has_no_bg_option():
+    result = CliRunner().invoke(search_group, ["google", "--help"])
+
+    assert result.exit_code == 0
+    assert "--bg" not in result.output
+
 # ---------------------------------------------------------------------------
 # navigate commands — with tab_id argument
 # ---------------------------------------------------------------------------