Tell a running daemon to drop its in-memory read cache (SessionCache).
Returns true if a daemon was reached. Never auto-starts a daemon — if none
is running there is no cache to flush. Force-rebuild CLI commands call this so
ctx_read map/signatures stop serving pre-rebuild output from the daemon’s
long-lived cache, which CLI index rebuilds otherwise can’t reach (#420).
Blocking helper for CLI commands: calls a daemon tool if the daemon is running.
Returns None if the daemon is not running or the call fails.
Attempts to auto-start the daemon if it’s not already running.