fix(of): correct vigil_feast's justification for of-nativity-vigil

The prior comment claimed of-nativity-vigil is 'not a distinct celebration' -
wrong: Temporal_of.named (temporal_of.ml:230) constructs it as its own
Sollemnitas-rank candidate on 24 December, a genuine contestant in
band/Precedence.resolve.

The real reason None is safe is structural, not that. The Nativity is
Tabula entry 2 (band 20); only entry 1, the Paschal Triduum (band 10),
bands lower. The Triduum's Easter-2..Easter window is confined to 20
March-25 April because Gregorian Easter never falls outside [22 March, 25
April] over the whole 1583-9999 domain (measured exhaustively in
test_computus.ml, not assumed), so it can never reach 25 December. The
Nativity therefore always keeps its own day and its vigil can never be
orphaned by a transfer or reduction.

Behaviour is unchanged: vigil_feast still returns None unconditionally.
RG 33 (EF-only) and Normae nn. 11/13 remain the reason the hook exists at
all and returns None for every other candidate.

0 files changed, 0 insertions, 0 deletions