refactor(session): simplify traversal guard to a helper + logger, harden non-leading separators

Follow-up to the salvaged #9560 fix:
- Replace the _TRAVERSAL_RE regex with an explicit _is_path_unsafe() helper
  (drops the now-unused `import re`); catches a path separator ANYWHERE,
  not just leading, so a non-leading Windows backslash can't slip through.
- Switch the per-entry skip in _ensure_loaded_locked from print() to
  logger.warning to match the module's logging conventions.
- Add AUTHOR_MAP entry for the contributor.
- Add regression tests for the non-leading-separator case.

scripts/release.py

@@ -45,6 +45,7 @@ ACP_REGISTRY_MANIFEST = REPO_ROOT / "acp_registry" / "agent.json"
 
 # Auto-extracted from noreply emails + manual overrides
 AUTHOR_MAP = {
+    "mediratta01.pally@gmail.com": "orbisai0security",  # PR #9560 salvage (session.py path-traversal guard, V-009)
     "panghuer023@users.noreply.github.com": "panghuer023",  # PR #37994 salvage (interrupt unblocks pending gateway approval; #8697)
     "w.a.t.s.o.n.mk10@gmail.com": "natehale",  # PR #48678 salvage (typing indicator lingers after final reply)
     "0x0sec@gmail.com": "kn8-codes",  # PR #48422 salvage (rich messages opt-in default off)