Per Opus pre-release verdict on PR #1843: the four handle_kanban_*
entry points declare '-> bool' but actually return True | None | False
(after PR #1843 made the False-vs-None distinction load-bearing for
the caller's '_kanban_unknown_endpoint' decision). Update the type
annotations to 'bool | None' and add a docstring on handle_kanban_get
(with cross-references on the three siblings) so a future contributor
adding a new return path doesn't accidentally produce a 0/'' value
that would silently revert the double-404 fix.
Test-only verification: kanban tests pass (49/49). Production behavior
unchanged. Cheap defensive cleanup per Nathan's standing absorb-in-release
default for ≤20-LOC documentation/type-annotation fixes.
5f6a55185c