test: review round 1 of Issue #71 (names, row-less stop server, migration retry)

- create with a non-ASCII name: the attach target is the name herdr has;
  bash/Python parity for non-ASCII and option-like names; no python3 is
  an error for a non-ASCII name.
- row-less stop without --herdr-session uses HERDR_SESSION_NAME; an
  unreadable row is not taken for no row.
- a retry (entry point, or any write) repairs a YAML a failed migration
  left in format 1.
- tier3: the "cannot infer agent" case registers its row, as tier1 does.
- S11: base re-pinned to 5cd72d2, which changes the shim's sanitize body.

Refs #71

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_issue23_24_startup_path.py

@@ -303,7 +303,7 @@ def test_s11_this_branch_does_not_change_the_generated_shim(mam_sandbox):
     too (one sanitize definition written in with `declare -f`, agent attach
     resolved, no silent wrong name), so the base is that commit."""
     repo = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
-    base = os.environ.get("MAM_BASE_SHA", "4243da5")
+    base = os.environ.get("MAM_BASE_SHA", "5cd72d2")
     show = subprocess.run(["git", "show", "%s:.agents/skills/lib.sh" % base],
                           capture_output=True, text=True, cwd=repo)
     if show.returncode != 0: