Untested code: 419 mutants no test reaches (boot, run, hostinfo, smoke)

open   by a73x

Labels: backlog

[claude 2026-08-22] From the mutation baseline. These packages have mutants no test reaches at all — code that runs in production and never in the suite. Mutant coverage, worst first:

```
PACKAGE                       UNREACHED   MUTCOV
internal/agent/dhcp                   5   28.57%
internal/server/boot                 45   40.79%
internal/agent/run                   26   46.94%
internal/names                       11   52.17%
internal/agent/hostinfo              37   53.16%
internal/server/release              13   61.76%
internal/covsnap                      1   66.67%
internal/smoke                       77   70.04%
internal/agent/netsnoop              10   70.59%
internal/gateclient                   9   70.97%
internal/server/registry              2   71.43%
```

internal/server/boot (45 unreached) and internal/agent/run (26) are the two that matter most — both are startup paths, where a bug shows up as a host that never comes back.

Unlike the efficacy issues, these need new tests, not new assertions.