fix: tighten APPMAP env var filter to avoid matching APPMAPX_* etc.

Addresses Copilot review feedback on #386: startswith(("APPMAP",
"_APPMAP")) also matched unrelated variables like APPMAPX_FOO. Match
the exact APPMAP/_APPMAP names plus the APPMAP_/_APPMAP_ prefixes
instead.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014Nw1eEFHvABs5hdjMej5bf

Author: claude

_appmap/configuration.py

@@ -511,6 +511,10 @@ def initialize():
     # Only log AppMap's own settings, never the full environment: arbitrary
     # environment variables (API keys, credentials, tokens, etc.) must never
     # end up in application logs.
-    appmap_env = {k: v for k, v in os.environ.items() if k.startswith(("APPMAP", "_APPMAP"))}
+    appmap_env = {
+        k: v
+        for k, v in os.environ.items()
+        if k in ("APPMAP", "_APPMAP") or k.startswith(("APPMAP_", "_APPMAP_"))
+    }
     logger.info("env: %r", appmap_env)
     os.environ["_APPMAP_MESSAGES_SHOWN"] = "true"