coli: consume the engine's TIERS line at startup so it doesn't leak into the first answer

After the READY handshake, run_serve emits one TIERS status line (the
web-dashboard expert-pyramid snapshot). cmd_chat never read it, so in
interactive chat it surfaced as literal "TIERS 0 181 19275 0.00 ..." text
prepended to the first response. Read and discard that one line after READY,
matching how the other status frames are consumed. Chat-only; the HTTP serve
path already drains it.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

c/coli

@@ -438,6 +438,8 @@ def cmd_chat(a):
         try: errlog.write(p.stderr.read().decode("utf-8","replace"))
         except (OSError, ValueError): pass
         errlog.seek(0); print(errlog.read()[-1500:]); sys.exit("the engine exited while loading")
+    p.stdout.readline()   # TIERS line (web-dashboard protocol): emitted once right after STAT;
+                          # left unread it leaks into the first answer's text
     # READY received. Drain the child's stderr into errlog without blocking:
     # the engine is still alive (blocked on stdin), so a plain read() would
     # hang forever waiting for EOF. A short bounded drain grabs the ~400 bytes