Function fold_mount_source 

fn fold_mount_source(source: &str) -> String

Canonical form of a mount source for comparison.

Case folding is Windows-only, deliberately (codex P2 on PR #2933). Docker on Windows can report a differently-cased drive letter than we asked for, so a case-sensitive compare there produces phantom drift and a needless recreate. Folding UNCONDITIONALLY is the opposite bug: on a case-sensitive host, switching an agent’s workspace from /work/Foo to the genuinely different /work/foo would look like a match, ensure_running would skip the recreate, and /workspace would keep serving the old directory.