fix(hy3): route H1/H2 DQ detail to the matching slot for a prelim+finals double-DQ

[fsalum]

Stacked on #29 ("type Event.distance as float for non-integer distances").
This branch is based on #29's branch, so #29 needs to merge first. Until it
does, this PR shows #29's commit alongside its own; after #29 lands it collapses
to the single DQ-parser commit (h_dq_parsers.py + its test).

Problem

h1_parser raises AssertionError("DQ Codes should match in the H1 line") on
any swim disqualified in both prelims and finals of the same event for
different infractions — a common case in IM events and championship
prelims/finals formats.

Such a swim's prelim and finals arrive as separate E1/E2 records that resolve
to one shared EventEntry carrying both prelim_dq_info and finals_dq_info.
h1_parser resolves the H1 detail line to a slot by fixed
finals -> swimoff -> prelim priority, takes the first populated slot, and
then asserts that slot's stored DQ code equals the H1's own code. Records arrive
finals-first, so by the time the prelim's H1 is parsed the finals slot is
already populated with a different code:

E2F …Q7T   -> finals slot code = 7T
H17T…      -> finals slot set, 7T == 7T ✓  (attaches to finals)
E2P …Q1M   -> prelim slot code = 1M
H11M…      -> resolves finals-first, takes finals (7T); 7T != 1M -> AssertionError

The assertion aborts the H1 line and the prelim DQ's human-readable reason
string is lost.

Two related latent defects sit behind the visible assertion:

1. When the two slots happen to share a DQ code the assertion does not fire,
   but finals-first resolution still attaches the reason to the wrong slot (both
   H1s land on finals).
2. h2_parser uses the identical finals-first resolution with no assertion at
   all, so H2 detail text is silently mis-attributed in the same double-DQ case.

Fix

h1_parser now resolves to the slot whose stored DQ code matches the H1's
own code, preferring a slot not yet filled so the two H1s of a same-code
double-DQ fill their own slots in file order. When no populated, unfilled slot's
code matches, it degrades to a no-op — the same graceful behavior the existing
no-slot guard already used (the DQ status and code are recorded by the E2/F2
result line regardless, so only the reason string is ever at stake). The
assert is removed.

h2_parser cannot match on its own code — an H2's 2-char code is the specific
stroke/leg infraction (e.g. 2L), not the slot's DisqualificationCode (e.g.
the relay-leg code 6A). So h1_parser records the slot it resolved (in the
opts dict threaded through every line parser) and h2_parser attaches its
detail to that same slot, falling back to the first populated slot when no H1
preceded it.

Tests

Added to tests/hy3/line_parsers/test_h_dq_parsers.py:

• prelim/finals H1s of a different-code double-DQ each route to their own slot
  (previously raised);
• same-code double-DQ fills each slot in file order rather than finals twice;
• an H1 whose code matches no populated slot is a no-op, not a raise;
• a relay leg code (6A) still attaches;
• an H2's detail follows its immediately-preceding H1's slot across a double-DQ.

All existing DQ-parser tests continue to pass.