Built-in agent CLIs are a machine-level fact, but runtime registration is
per-workspace, and every registration re-ran `<cli> --version` for every
configured agent. A daemon serving N workspaces spawned N×M probe processes at
startup instead of M (24 workspaces × 5 agents = 120 instead of 5).
- Detect the built-in payload once per workspace-sync batch and reuse it for
every workspace that sync registers. Nothing is cached on the Daemon, so
standalone re-registrations still re-probe and an in-place CLI upgrade is
still reported with its current version. The probe is lazy: a steady-state
sync with nothing to register never shells out.
- Retry a failed provider's probe once inside the round before dropping it,
so one transient failure can't cost every workspace in the batch that
runtime. Only failed providers retry, so the round stays O(M).
- Time each attempt across resolve + detect, so a slow probe inside the
MUL-4486 self-heal is not misread as a fast failure and retried.
Fixes#5837
Co-authored-by: multica-agent <github@multica.ai>