refact(deployer): one MainPID gate for all three LLM endpoints

frank-dragoon's health gate never checked WHO answered :7770 — the
false-green the fleet learned about on 2026-09-26 (a stray probe holding
the port satisfies a bare curl while the unit is stopped). The other two
handlers carried that check as inlined copies; all three now call
assert_unit_owns_port, and dragoon gets the protection it was missing.

The seam follows: the endpoints' text-grep deployer tests are deleted,
because tests/llm_deploy_gates.bats EXECUTES the same handlers end to end
(stub systemctl/podman/sudo/ss/curl) and asserts refusals, restarts, unit
links, the pending marker, and the MainPID hardening. GATE_PREFIX is
exported at each handler for the same reason the serve scripts export it.

scripts/lib/llm-gates.sh

@@ -32,7 +32,10 @@
 # writes the error body as the artifact), and the declared byte count is a
 # contract in both directions — a bigger file is a DIFFERENT artifact.
 
-# GATE_PREFIX names the endpoint in every refusal (e.g. frank-dragoon).
+# GATE_PREFIX names the endpoint in every refusal (e.g. frank-dragoon). The
+# caller exports it; shellcheck cannot follow it across the source boundary,
+# so the read site carries the directive.
+# shellcheck disable=SC2034
 : "${GATE_PREFIX:=gate}"
 
 # Two bash laws make the `return 1` at every call site load-bearing: