perf: skip blank page on first browser command

[jackwener]

Summary

• Eliminate the about:blank → target-domain navigation on first command execution, saving ~1-3s
• Extension's getAutomationWindow() now accepts an optional initialUrl to create the window directly on the target domain
• CLI removes the isAlreadyOnDomain() exec-based check and always calls page.goto() — the extension's handleNavigate already fast-paths when the tab is at the target URL

How it works

Before:

1. CLI: exec getCurrentUrl() → triggers window creation with about:blank
2. CLI: detects URL mismatch → calls goto(targetDomain)
3. Extension: navigates about:blank → targetDomain (1-3s page load)
4. Command runs

After:

1. CLI: calls goto(targetDomain) directly
2. Extension: creates window with targetDomain as initial URL
3. handleNavigate detects tab already at target → fast-path return
4. Command runs

Changes

• extension/src/background.ts: getAutomationWindow(workspace, initialUrl?) uses target URL for window creation; resolveTabId and handleNavigate pass URL through
• src/execution.ts: Remove isAlreadyOnDomain() check, always navigate directly. Extension handles domain-match efficiently

Test plan

• npx tsc --noEmit passes (both CLI and extension)
• All 143 unit test files pass (1033 tests)
• Subsequent commands still skip redundant navigation (extension fast-path)
• Manual test: verify first command loads directly to target domain without blank page flash