test(temporal-ef): extend the anchors-erosion guard to fixed-date anchors

The guard added under Plan 2's carried item 5 only scanned a +/-window of
dates around Easter, so it caught erosion of an Easter-relative anchor but
missed a fixed-date one entirely: deleting ("ef-nativity", ...),
("ef-epiphany", ...) or ("ef-christ-the-king", ...) from temporal_ef.ml's
anchors list left the whole suite green. Item 5 -- the item this guard
exists to satisfy -- was therefore only half-closed while being reported
as closed, and the least-covered anchor was exactly the one with the
weakest citation (Christ the King's last-Sunday-of-October placement,
oracle-backed but not yet primary-verified as of this commit).

Widened the scan from an Easter-centred window to the whole civil year:
named only ever answers Some for its ~20 genuinely proper/named days, so
scanning every day of the year is no more likely to pick up an ordinary
week's slug by accident than the narrower window was -- it is simply no
longer selective about which KIND of named day it notices. Renamed
easter_relative_named_slugs to named_slugs_for_year and the covering test
to test_anchors_cover_all_named_days accordingly; broadened the negative
fixture (test_anchors_erosion_is_caught) to strike an Easter-relative and
a fixed-date anchor together.

Verified by deleting each of the three previously-unguarded anchors in
turn (locally, reverted after each), rebuilding and re-running the suite:

  delete ef-nativity:        Received: `["ef-nativity"]'
  delete ef-epiphany:        Received: `["ef-epiphany"]'
  delete ef-christ-the-king: Received: `["ef-christ-the-king"]'

each against the same assertion:

  ASSERT 1598: every named slug is restated in anchors
  FAIL 1598: every named slug is restated in anchors
     Expected: `[]'

All three reversions applied only to temporal_ef.ml (not committed); the
tree is unchanged there. Test count unchanged (259); no behaviour change.

0 files changed, 0 insertions, 0 deletions