What changed

• Add an optional external presenter for Plannotator's local review URL.
• Use it across the shared server and Pi extension before opening the default browser.
• Close the exact external presentation when its Plannotator session stops.
• Keep the existing browser behavior when no presenter is configured or presentation fails.

Why

Terminal environments such as Herdr already have their own browser surface. This lets them display Plannotator's existing page there without moving approvals, feedback, or agent behavior out of Plannotator.

The presenter is a small executable configured in config.json. Plannotator sends it one JSON request to present the URL and another to dismiss the returned handle. Plannotator does not depend on Herdr.

Verification

• 329 relevant server, hook, Pi, and presenter tests pass.
• TypeScript checks pass across the workspace.
• The companion Herdr plugin was proven end to end: configure, open the local page, return the pane handle, and dismiss that exact pane.

Companion plugin: https://github.com/plannotator/herdr-plannotator