fix(ego-browser): refresh session after opening tab

[mameikagou]

Summary

• invalidate the cached CDP session after newTab() creates a target
• prefer the created target for the next page-scoped CDP command
• add a regression test that starts on an old session and verifies the next command attaches to the new target

Why

newTab() returned the new target ID without updating session selection. Because ensureSession() caches the current session for two seconds, an immediate wait or page command could continue operating on the previously active tab. switchTab() already invalidates the session and sets a preferred target; this applies the same transition after native tab creation.

Impact

Commands issued immediately after newTab() or the new-tab branch of openOrReuseTab() now attach to the created tab instead of briefly reusing the prior tab's session.

Validation

• npm test — 312 tests passed
• Prettier check passed
• TypeScript typecheck passed
• Site-skill validation passed
• Vulnerability audit found 0 issues
• Real-browser navigation helper case passed; the full local E2E run finished 42/45, with unrelated existing/environmental failures in ffmpeg discovery, the concert inventory fixture, and canvas zigzag stroke counting