refactor(acp): share interrupt-sentinel prefix, simplify guard

Replace the ACP-local prefix/suffix matcher + helper with a single
startswith() check against INTERRUPT_WAITING_FOR_MODEL_PREFIX, now
defined once in conversation_loop.py where the sentinel is produced.
Keeps the source of truth in one place so the guard cannot drift if
the status string changes. Net -17 LOC in server.py.

Also add lsaether to release.py AUTHOR_MAP.

scripts/release.py

@@ -65,6 +65,7 @@ AUTHOR_MAP = {
     "290859878+synapsesx@users.noreply.github.com": "synapsesx",
     "dirtyren@users.noreply.github.com": "dirtyren",
     "islam666@users.noreply.github.com": "islam666",
+    "25539605+lsaether@users.noreply.github.com": "lsaether",
     "zhaolei.vc@bytedance.com": "zhaoleibd",
     "jeffrobodie@gmail.com": "jeffrobodie-glitch",
     "kyssta-exe@users.noreply.github.com": "kyssta-exe",