hive-agent-forge-token and hive-agent-queue-credential both run with
UMask=0377. Their scripts captured bao's stderr in `err="$(mktemp)"`,
which under that umask is created 0400; the very next `2>"$err"` on the
`bao login` line cannot reopen it for writing, so bash fails the
redirect with "Permission denied" before bao ever runs. The `if !`
around the login then took the only error branch it had and printed
"this agent's certificate was refused by the swarm secret store" — the
store was never contacted. No agent has fetched either credential.
The stderr file now lives in each unit's own 0700 RuntimeDirectory and
is removed before every redirect into it, so the redirect creates it —
the idiom forge-token.nix already used for its staging file.
The login's error branch now says which of these happened, then quotes
bao's output:
- `$err` could not be created, so bao never ran;
- the store answered with HTTP 4xx (refusal) or another status;
- the store sent a TLS alert rejecting the certificate;
- no answer at all (network, DNS, or local TLS).
Unreadable cert/key credentials are reported before bao runs.
bao.nix has the same fetch shape but no UMask=, so its mktemp file is
0600 and writable; it is untouched.
Closes#4735
forge-token.nix fetches swarm/agents/<agent>/forge-token under the
agent's own store identity into /run/hive-agent-forge-token/token, and
re-fetches on a timer so a rotation lands. hive-forge, the git
credential helper, hive-forge-notify, forge-avatar-sync and the web UI
read that file first and fall back to <state>/forge-token.
tea-login is deleted: it copied the token into ~/.config/tea, which
docs/swarm/credentials.md forbids for a store secret. hive-forge covers
the same verbs. swarmctl gains agent mint-forge-token.
Refs #3782
