Watch mode for the CLI

This release is all about the local loop. The CLI is where most Relay time is spent, so we made it faster and less repetitive.

#Added

• Watch mode. relay dev --watch restarts your routes on file save, keeping the tunnel and request history alive across restarts. Median reload is under 300 ms.
• Request replay. Press r in the dev console to replay the last request, or relay replay <id> to re-send anything from the request log. Great for iterating on a handler without leaving the editor.

#Improved

• Cold starts for deployed routes are 40 percent faster after we moved dependency resolution to build time.
• relay logs now streams with structured fields and supports --filter status>=500.

#Fixed

• The dev tunnel no longer drops connections when your machine sleeps and wakes; it reconnects with the same public URL.
• Fixed a case where relay deploy reported success but skipped routes whose filenames contained brackets.