Fix AssetRegistry URL lookups by type

[puneetdixit200]

Description

Store all assets registered for the same file URL so AssetRegistry#getByUrl(url, type) can return the asset matching a requested type. Untyped getByUrl(url) keeps the existing last-added behavior for compatibility.

Fixes #8489

Testing

• npm test -- test/framework/asset/asset-registry.test.mjs --grep "#getByUrl"
• npm test -- test/framework/asset/asset-registry.test.mjs
• npm run lint
• npm run build:types
• npm run test:types
• git diff --check

Checklist

• I have read the contributing guidelines
• My code follows the project's coding standards
• This PR focuses on a single change

[Maksims]

Please replace with a simple for..of loop, with early return inside of it.

[mvaligursky]

🤖 Automated PR review — posted on my behalf by Claude Code (Opus 4.8). Not a human review; flagging for awareness.

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Looks correct and well-tested. Untyped getByUrl(url) preserves the last-added semantics (Set iteration is insertion order, forEach keeps overwriting result), all external callers go through the public method, and the Set-per-url removal is actually more correct than the old map — removing one of two assets sharing a url no longer wipes the other. Nothing blocking. Two minor notes:

1. getByUrl iterates the whole set with no early exit and returns the last match. That's intentional to keep untyped compat, but for the typed branch a for...of with an early break would be cheaper and clearer about intent (and would return the first match of that type). Sets are tiny so the perf difference is negligible — purely a readability nit.

2. Pre-existing (not introduced here), but now more relevant: the registry indexes by asset.file.url at add time and never re-indexes if file.url changes later (remove then uses the current url, so a changed-url asset leaves a stale set entry). Harmless single-asset before; with multiple assets per url now supported, a stale entry could shadow a live one. Out of scope for this PR — just flagging in case it's worth a follow-up.