fix(spawn): strip ANSI codes from zellij list-sessions output

Zellij outputs colored text with ANSI escape codes, which caused
session name parsing to fail. Now strips escape codes before parsing.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

amc_server/mixins/spawn.py

@@ -99,9 +99,11 @@ class SpawnMixin:
 
         try:
             # Check rate limit inside lock
+            # Use None sentinel to distinguish "never spawned" from "spawned at time 0"
+            # (time.monotonic() can be close to 0 on fresh process start)
             now = time.monotonic()
-            last_spawn = _spawn_timestamps.get(project, 0)
-            if now - last_spawn < SPAWN_COOLDOWN_SEC:
+            last_spawn = _spawn_timestamps.get(project)
+            if last_spawn is not None and now - last_spawn < SPAWN_COOLDOWN_SEC:
                 remaining = SPAWN_COOLDOWN_SEC - (now - last_spawn)
                 self._send_json(429, {
                     'ok': False,
@@ -177,8 +179,11 @@ class SpawnMixin:
             )
             if result.returncode != 0:
                 return False
+            # Strip ANSI escape codes (Zellij outputs colored text)
+            ansi_pattern = re.compile(r'\x1b\[[0-9;]*m')
+            output = ansi_pattern.sub('', result.stdout)
             # Parse line-by-line to avoid substring false positives
-            for line in result.stdout.splitlines():
+            for line in output.splitlines():
                 # Zellij outputs "session_name [Created ...]" or just "session_name"
                 session_name = line.strip().split()[0] if line.strip() else ''
                 if session_name == ZELLIJ_SESSION: