Bundles v0.5.2 task set (38, 39, 42, 43, 55, 56, 59, 62, 67) and
v0.5.3 task set (50, 58, 60, 61) under one tag. Covers v0.5.1..HEAD.
v0.5.2 was committed but never tagged separately — folded in here
rather than retroactively labeling.

Non-breaking; all touched modules ≥80% coverage; dialyzer + credo
clean on touched files.