[chore] converters: typed InvalidIdentifierError from require_uuid + log the orchestrator drop (#25)

require_uuid raised a bare ValueError('UUID value cannot be None'), so a
malformed/None identifier propagated as an opaque error callers either let
500 or broad-catch-and-silently-swallow — the orchestrator reaper call site
wrapped it in a bare except-Exception return with NO log, dropping a bad
task_id_str invisibly. Introduce InvalidIdentifierError(ValueError) and
raise it from require_uuid for both None and unparseable input; it stays a
ValueError subclass so existing except-ValueError / except-Exception callers
are unaffected, but typed so a caller can handle a bad identifier distinctly.
The reaper now catches the typed error, logs at warning, and no-ops — the
drop is visible instead of swallowed.

Tests: None and an unparseable string both raise InvalidIdentifierError; it
subclasses ValueError (back-comat).

tests/unit/utils/test_converters.py

@@ -6,6 +6,7 @@ from uuid import uuid4
 
 import pytest
 from roboco.utils.converters import (
+    InvalidIdentifierError,
     require_uuid,
     to_python_uuid,
     to_python_uuid_list,
@@ -27,6 +28,27 @@ def test_require_uuid_raises_for_none() -> None:
         require_uuid(None)
 
 
+def test_require_uuid_none_raises_typed_identifier_error() -> None:
+    """#25: a None identifier raises the typed InvalidIdentifierError (a
+    ValueError subclass), not a bare ValueError, so callers can distinguish a
+    bad identifier from any other exception instead of broad-catching."""
+    with pytest.raises(InvalidIdentifierError, match="cannot be None"):
+        require_uuid(None)
+
+
+def test_require_uuid_unparseable_raises_typed_identifier_error() -> None:
+    """#25: an unparseable identifier raises InvalidIdentifierError, not a bare
+    ValueError — the dropped-identifier pattern must surface as a typed error."""
+    with pytest.raises(InvalidIdentifierError, match="invalid UUID identifier"):
+        require_uuid("not-a-uuid")
+
+
+def test_invalid_identifier_error_is_value_error() -> None:
+    """Back-compat: InvalidIdentifierError subclasses ValueError so existing
+    `except ValueError` callers keep catching it."""
+    assert issubclass(InvalidIdentifierError, ValueError)
+
+
 def test_to_python_uuid_returns_none_for_none() -> None:
     assert to_python_uuid(None) is None