feat(#731): delegate title matching to core SimilarityEngine

[chubes4]

Summary

Migrates data-machine-events to use the unified SimilarityEngine from core (data-machine#731, data-machine#732) instead of maintaining its own duplicate title normalization and fuzzy matching.

• EventIdentifierGenerator rewritten as thin wrapper — extractCoreTitle(), titlesMatch(), normalize_dashes(), normalize_text() all delegate to SimilarityEngine. Venue matching stays (domain-specific, not in core).
• DuplicateDetectionAbilities — removed data-machine-events/titles-match ability (superseded by core's datamachine/titles-match). Added event strategy registration on datamachine_duplicate_strategies filter.
• EventUpsert and CheckDuplicatesCommand — no changes needed (they call EventIdentifierGenerator, which now delegates).

What Changed

File	Change
inc/Utilities/EventIdentifierGenerator.php	Thin wrapper → SimilarityEngine for title ops; venue matching stays
inc/Abilities/DuplicateDetectionAbilities.php	Removed titles-match ability; added datamachine_duplicate_strategies filter registration
tests/Unit/EventIdentifierGeneratorTest.php	Fixed broken test, added venue + delegation tests

Strategy Registration

The events plugin now registers on core's datamachine_duplicate_strategies filter:

add_filter( 'datamachine_duplicate_strategies', function( $strategies ) {
    $strategies[] = [
        'id'        => 'event_venue_date_title',
        'post_type' => 'event',
        'callback'  => [ DuplicateDetectionAbilities::class, 'executeEventStrategy' ],
        'priority'  => 10,
    ];
    return $strategies;
});

When core's datamachine/check-duplicate is called for the event post type with context.venue and context.startDate, this strategy fires first — using venue + date + fuzzy title matching.

Code Removed

• normalize_dashes() — was identical copy of core's implementation
• normalize_text() — replaced by SimilarityEngine::normalizeBasic()
• extractCoreTitle() body — replaced by SimilarityEngine::normalizeTitle()
• titlesMatch() body — replaced by SimilarityEngine::titlesMatch()
• data-machine-events/titles-match ability — superseded by datamachine/titles-match

Test Fix

test_rightmost_delimiter_used was renamed to test_earliest_delimiter_used — the old test asserted behavior inconsistent with the actual leftmost-wins algorithm (the test would have failed if CI were running). New test correctly asserts that ': ' at position 8 wins over ' - ' at position 20.

Dependency

Requires data-machine >= 0.39.0 (SimilarityEngine + DuplicateCheckAbility from PR #732).

Relates to Extra-Chill/data-machine#731