refact(deploy-remote): shared root-unit start, config copy, retire helpers

rank 5. The three LLM handlers duplicated the same tail (relink,
daemon-reload, enable, restart, /health gate, MainPID port proof) ->
start_root_unit SERVICE PORT LIMIT; frank-archon's bespoke 900-iteration
loop was exactly wait_for_health at limit 900. copy_config DEST SRC...
replaces five hand-rolled mkdir+cp pairs (loki, alloy, grafana x2);
retire_unit_file PATH TRASH [UNIT] replaces the duplicated compose-era
unit retirements (halogen dragoon quadlet, comfyui.service). The health
grep seam now pins the per-endpoint call (start_root_unit frank-dragoon
7770).

tests/deployment_flow.bats

@@ -78,7 +78,10 @@ load helpers
 }
 
 @test "remote runner health-checks an inference endpoint" {
-    grep -q '127.0.0.1:7770/health' "$REPO_ROOT/scripts/deploy-remote.sh"
+    # start_root_unit carries the health gate for all three LLM units; the
+    # contract is that each endpoint's start names its port, and 7770 is
+    # frank-dragoon's.
+    grep -q 'start_root_unit frank-dragoon 7770' "$REPO_ROOT/scripts/deploy-remote.sh"
 }
 
 @test "deploy.sh pulls the merged checkout on the target" {