`agent-<hive>` reads as "the agent named <hive>" — which is the one thing that
identity does not carry, since it is minted per hive. It becomes
`hive-<hive>-agent`: the hive's own id, extended.
The rename is not a string swap. `hive-foo-agent` satisfies the hive parse too
(it strips to a hive named `foo-agent`), so the responder's agent rule now runs
BEFORE its hive rule — most specific wins. Hive-first would have handed every
agent its hive's grant, including writing that hive's status key, with nothing
to report it: the client authenticates and is merely able to do more than it
should.
`Policy::new`'s overlap check goes with the prefix it was written for. The
invariant the suffix form needs instead is that the suffix is non-empty: an
empty one makes `strip_suffix` succeed on every hive id, so the two principals
become one string and whichever arm runs first answers for both.
The suffix form also introduces a collision the prefix form did not have: a hive
genuinely named `foo-agent` mints `hive-foo-agent`, which is hive `foo`'s agent
id. The responder cannot see it — it has no roster, deliberately — so
`swarm-authelia.nix` asserts at eval that no hive name ends with the suffix. The
existing duplicate-id assertion does not cover this: it fires only when both
`foo` and `foo-agent` are on the roster, and with `foo-agent` alone there is no
duplicate, just a hive quietly receiving its agents' grant.
A test written by analogy with `the_prefix_alone_names_no_hive` failed, correctly
— `hive--agent` is a hive named `-agent` under the hive parse, which this module
cannot rule out. It now asserts only the part this module owns: no empty hive
name is ever expanded into a subject.
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