* fix(server): back off degraded git polling on an unchanged workspace
When the recursive watcher declines a repository (over 250,000 entries on
macOS/Windows, or any watcher setup failure), WorkspaceGit falls back to
polling. That fallback rescheduled itself every 5 seconds for as long as the
workspace existed, with no client or agent involved. On a repository large
enough to defeat the watcher each tick is an expensive `git status`, so the
daemon held about a core indefinitely.
Double the gap after every tick whose workspace snapshot came back identical,
up to a 60-second ceiling, and reset to the 5-second base on the first change.
Both degraded loops — working tree and repository metadata — share the rule.
Explicit reads still force a refresh, so the ceiling only bounds how long an
edit made outside Paseo stays undiscovered.
Fixes#5102
* test(server): cover repository-metadata degraded backoff, document failed-tick semantics
* test(server): drive the recovery-refresh assertion off the fake clock, not waitFor
* test(server): declare metadata poll counter as a function