loadConfig() calls isGitIgnored() which spawns a git check-ignore
subprocess. The result is stable for the process lifetime but was
being recomputed on every call. With 28+ loadConfig call sites, this
could spawn multiple redundant git subprocesses per CLI invocation.
A module-level Map cache keyed on (cwd, targetPath) ensures the
subprocess fires at most once per unique pair per process.
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>