perf: store components in archetype-indexed slices instead of maps

[ragoune]

ComponentsStorage kept its component columns in a map[archetypeId][]T, hashing on every storage access. archetypeId is dense, so the columns are now held in a [][]T indexed directly by archetypeId, removing the hash from every add, remove, copy and query read.

Query columns are fetched through a bounds-safe getColumn: a query with an optional component matches archetypes that don't contain it, whose id can be beyond that component's column slice — a raw index would panic (a map returned nil). getColumn is kept out of line (//go:noinline) so it does not perturb the hot loops; this also makes iteration slightly faster than the previous map.

The query Foreach loops gain a fast path for the common case where all columns are present, hoisting the per-entity nil checks (needed only for optional components) out of the loop.

[codecov]

Codecov Report

❌ Patch coverage is 94.48819% with 7 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
storage.go	63.15%	7 Missing ⚠️

Files with missing lines	Coverage Δ
query.go	86.30% <100.00%> (ø)
storage.go	63.33% <63.15%> (-0.67%)	⬇️

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