Quieter background preview polling

Reduces repeated background work while looking for local development servers. Preview discovery scans less often when idle, shares recent readiness checks, and responds to process changes in T3-managed terminals. Servers started elsewhere remain discoverable through periodic scans, without a system-wide process sweep every few seconds.

Branch

GitHubfix/reduce-background-git-ref-port-polling

PR

…

Status

Rejected

Reason

Upstream requires changes like this to be discussed and pre-approved before a pull request is opened, and I do not get enough out of it personally to justify going through that process.