fix(extension): detect browser error pages earlier

- Add shared browser error URL detection for Chrome, Edge, Brave, and Firefox-style about:error pages.
- Short-circuit read-only DOM and HTML commands with safe fallbacks when tabs are already on browser error pages.
- Fail navigation waits, DOM waits, polling, and URL watches with clearer error-page messages.
- Bump package and extension version to 0.9.8 and extend regression coverage for cross-browser error-page handling.

tests/test_extension_error_page_handling.py

@@ -5,8 +5,13 @@ ROOT = Path(__file__).resolve().parents[1]
 def test_extension_retries_error_page_script_injection_before_failing():
     core = (ROOT / "extension" / "src" / "core.ts").read_text()
 
+    assert "isBrowserErrorUrl" in core
     assert "isErrorPageScriptError" in core
-    assert "chrome-error://chromewebdata" in core
+    assert "chrome-error://" in core
+    assert "edge-error://" in core
+    assert "brave-error://" in core
+    assert "about:neterror" in core
+    assert "about:certerror" in core
     assert "isTransientScriptError(e)" in core
 
 def test_read_only_dom_commands_have_error_page_fallbacks():
@@ -17,12 +22,16 @@ def test_read_only_dom_commands_have_error_page_fallbacks():
     assert "return false;" in dom
     assert 'case "domQuery":' in dom
     assert 'case "extractText":' in dom
+    assert "isBrowserErrorUrl(tabUrl)" in dom
     assert "isErrorPageScriptError(e)" in dom
 
-def test_tabs_watch_url_reports_last_seen_url_on_timeout():
+def test_navigation_and_tabs_report_browser_error_pages():
     tabs = (ROOT / "extension" / "src" / "commands" / "tabs.ts").read_text()
+    navigation = (ROOT / "extension" / "src" / "commands" / "navigation.ts").read_text()
 
     assert "lastUrl" in tabs
     assert "lastStatus" in tabs
     assert "showing an error page" in tabs
     assert "last URL:" in tabs
+    assert "isBrowserErrorUrl" in navigation
+    assert "showing an error page while waiting for load" in navigation