tool_groups::read and capabilities::read returned an empty map when
their file existed but didn't parse. Every set_*/remove_agent is a
read-modify-write, and write() rewrote the file in place, so a crash or
ENOSPC mid-write left a truncated file, and the next write (e.g. the
manager-spawn seed of ruth's tool groups) replaced it with a map holding
only one agent. The scheduling and approval gates then denied every
other agent, recoverable only from meta git history.
- Both registries now read through agent_config::read_map: a missing
file is still the empty map, any other read failure or a parse
failure is an io::Error. set_groups / set_caps / remove_agent fail
without writing.
- Writes go through agent_config::write_map: temp file in the same
directory, fsync, rename, fsync the directory. hive-c0re had no
shared atomic-write helper (the existing tmp+rename sites are inline
and don't fsync).
- Callers of read / groups_for / has_cap now handle the error:
* dashboard GET /api/tool-groups, /api/capabilities,
/api/permissions/stale return 500 instead of an empty table;
* the SSE permission snapshots are skipped with a warn;
* render_flake returns Result, so sync_agents fails instead of
rendering every agent without its tool groups / capabilities;
* set_nspawn_flags propagates has_cap's error;
* the socket tool-group gates deny with the read error as message;
* seed_manager_tool_groups logs and does not seed.
- capabilities::write had no callers left once set_caps writes through
write_map, and is removed.
Closes#4719
e0b08fe362