fix(agents): any spelling of a claude uuid is checked as claude's lowercase id (Issue #31, review)

_is_uuid took an uppercase or mixed-case uuid, and the paths built from it
are the live lowercase session's own files on macOS's default
case-insensitive APFS. The in-use checks compare exactly, though: session
files and command lines carry the lowercase id, so `purge claude <UPPER>`
found no holder and could remove a live session's files. _canonical now
lowercases a canonical uuid, and the paths, the session-file and job
matches, the in-use check and the residual all use it; a command line is
searched for both spellings.

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

tests/test_issue31_purge_residual.py

@@ -290,6 +290,43 @@ def test_claude_rejects_malformed_uuid(home, tmp_path, conv, bad):
     assert memory.exists() and all(p.exists() for p in named)
 
 
+@pytest.mark.parametrize("spell", [str.upper, lambda u: u[:18].upper() + u[18:]], ids=["upper", "mixed"])
+def test_any_spelling_of_the_uuid_is_the_lowercase_session(home, tmp_path, conv, live, spell):
+    """claude writes its ids in lowercase, and on macOS's default
+    case-insensitive APFS another spelling names the very same files. Every
+    check then uses the lowercase id: the live holder is seen, by its session
+    file or its command line, and a purge takes the session's own paths."""
+    ws = tmp_path / "ws"
+    ws.mkdir()
+    t = _tree(home, ws, conv, tmp_path / "ctmp", pid=live.pid)
+    other = spell(conv)
+    assert other != conv
+    adapter = get_adapter("claude")
+    ctx = _ctx(ws, home)
+
+    assert adapter.conversation_in_use(other, ctx) is True
+    for args in (["purge", "claude", other, str(ws)], ["in-use", "claude", other, str(ws)]):
+        res = _agents_cli(args, ws)
+        assert res.returncode == 4, res.stdout + res.stderr
+    assert all(p.exists() for p in t.values())
+
+    live.kill()
+    live.wait()
+    named = subprocess.Popen(["sh", "-c", "sleep 120", conv])
+    try:
+        time.sleep(0.05)
+        assert adapter.conversation_in_use(other, ctx) is True, "a command line naming the lowercase id"
+    finally:
+        named.kill()
+        named.wait()
+
+    assert adapter.has_artifacts(other, ctx) is True
+    purged = adapter.purge_artifacts(other, ctx)
+    assert not any(p.exists() for p in t.values()), {k: str(p) for k, p in t.items() if p.exists()}
+    assert purged and all(other not in p for p in purged)
+    assert adapter.residual_artifacts(other, ctx) == []
+
+
 def test_claude_purge_never_follows_a_linked_dir_below_a_root(home, tmp_path, conv):
     """A symlinked <key> (tmp, projects) or file-history/ below its root is
     not followed: what lies behind it stays and is reported as residual."""