re #96 add @template generics to univeros/structure collections

[tonydspaniard]

The big one — genericises the whole collection library (Map/Set/Vector/Deque/Stack/Queue/PriorityQueue/Pair) as one coherent, PHPDoc-only, runtime-safe refactor. Baseline phpstan-baseline.neon: 325 → 111 entries (−214), the bulk of the #96 level-6 burn-down.

@template scheme

• CollectionInterface<TKey, TValue> @extends Traversable<TKey, TValue>
• MapInterface<TKey, TValue>; SetInterface<TValue> / SequenceInterface<TValue> / VectorInterface<TValue> / Stack/Queue<TValue> @extends CollectionInterface<int, TValue>; PairInterface<TKey, TValue>; PriorityNodeInterface<TValue>
• concrete classes add @implements and pin the SPL generics (IteratorAggregate<…> / ArrayAccess<…>); Pair's promoted $key/$value get @var TKey/@var TValue (native mixed unchanged)
• traits carry their own @template and @use the base trait with bound args; $internal typed per storage shape

Correctness calls

• Object keys: Map allows arbitrary (incl. object) keys, so every toArray()/jsonSerialize() returning a PHP array is typed array<array-key, TValue> — not array<TKey, …>. TKey flows only through iteration.
• PHPDoc-only: no native type or native-property changes (avoids the uninitialised-property bug class). The one runtime touch is a behaviour-neutral $values ?? [] guard in Set::__construct for template inference.
• 4 documented @phpstan-ignore in CollectionTrait: the shared trait serves collections with different storage shapes, so the $internal = [] default can't match every narrowed @var and the capacity/append paths are unreachable for delegate-backed collections. Each annotated with a reason; masks no real bug (verified with reportUnmatchedIgnoredErrors).

Consumer impact (read this)

Generic base types mean subclasses/users must now specify args, so ~28 new "does not specify its types" findings appear in Cookie (+13), Container (+8), Http (+4), Courier, etc. Net is still −214. These are a clean mechanical follow-up: declare @extends Map<…> on the consumer collection classes — which also clears the MapInterface-return findings earlier chunks had to leave. I scoped them out to keep this core-library change reviewable on its own.

Verification

• composer stan green (111 baselined, 0 live), CS clean, rector --dry-run clean (after applying the configured-set cleanups the new types unlocked).
• Full suite: 5 pre-existing ext-mongodb errors, no regressions (the agent's 2724 Structure tests pass; I verified the whole suite since every package consumes these collections).

Part of #96. Progress: 719 → 111 (85% cleared.) Remaining: ~28 consumer @extends declarations + the small code-quality leftovers (unsafe new static, strict comparisons, subtype conflicts), then raise level 6 → 7 → 8.