fix: Restrict using slot for strings

[aleksanderkatan]

Includes changes from #2703 by @iwoplaza

[aleksanderkatan]

@pullfrog review

[pullfrog]

✅ No new issues found.

Reviewed changes — This PR prevents raw WGSL string injection through external maps, slots and TGSL expressions by requiring strings to carry a known schema type or be wrapped in a dedicated ResolvableString marker used for argument names.

• Adds ResolvableString to wrap raw-WGSL argument identifiers used during entry-function header generation.
• Tightens ResolutionCtx.resolve so that a bare string without a concrete schema throws a clear error instead of being injected.
• Replaces ctx.resolve(value, dataType).value calls with ctx.resolveSnippet across generation code for consistency.
• Removes strings from the isWgsl / Wgsl type union, since they are no longer first-class resolvable values.
• Adds tests covering direct, indirect, slot-based and TGSL string-injection cases, and updates existing slot tests to use d.v3f values instead of WGSL string snippets.

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[pullfrog]

✅ No new issues found.

Reviewed changes — This PR prevents raw WGSL string injection through external maps, slots and TGSL expressions by requiring strings to carry a known schema type or be wrapped in a dedicated ResolvableString marker used for argument names.

• Adds ResolvableString to wrap raw-WGSL argument identifiers used during entry-function header generation.
• Tightens ResolutionCtx.resolve so that a bare string without a concrete schema throws a clear error instead of being injected.
• Replaces ctx.resolve(value, dataType).value calls with ctx.resolveSnippet across generation code for consistency.
• Removes strings from the isWgsl / Wgsl type union, since they are no longer first-class resolvable values.
• Adds tests covering direct, indirect, slot-based and TGSL string-injection cases, and updates existing slot tests to use d.v3f values instead of WGSL string snippets.

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[pullfrog]

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[pullfrog]

Important

The runtime guard now rejects strings, but the Wgsl type still advertises them. Tightening the type would keep string-injection errors compile-time instead of runtime.

Reviewed changes — restrict raw string injection into WGSL and route internal identifier strings through a new ResolvableString wrapper.

• Introduced internal ResolvableString so raw-function positional argument names can still be emitted as valid WGSL identifiers.
• Updated ResolutionCtxImpl.resolve to throw when a string is resolved without a concrete schema, blocking string injection via externals, slots, and TGSL identifiers.
• Converted generator/accessor sites from ctx.resolve(value, dataType) to ctx.resolveSnippet(snippet).
• Updated tests to stop relying on string-valued slots and added coverage for the new restrictions plus a comptime-string-slot test.

⚠️ Wgsl type/runtime mismatch

packages/typegpu/src/types.ts:75 still defines Wgsl as Eventual<string | number | boolean | ResolvableObject>, but isWgsl at types.ts:425 no longer accepts strings. The mismatch means users can pass a string to resolveWithContext(...).externals or the low-level resolve(item: Wgsl, ...) and have it type-check but throw at runtime. Removing string from the Wgsl type would make this restriction compile-time.

⚠️ String injection still possible with a concrete schema

packages/typegpu/src/resolutionCtx.ts:961 throws for strings only when no schema (or UnknownData) is supplied, but the branch at resolutionCtx.ts:968 still returns snip(item, schema, 'runtime') when a concrete schema is provided. This is an internal hole in the "no raw strings" rule. If no internal call site depends on it, the branch should be removed; otherwise it warrants a comment explaining the legitimate use case.

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Unable to submit via the review API in this environment, so posting the review as a comment.

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[pullfrog]

Technical note: I attempted to submit the above feedback via create_pull_request_review multiple times, but the MCP tool consistently skipped because it did not receive the body/comments parameters from my calls. I was unable to get that tool to create an actual PR review in this run.

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[pullfrog]

✅ No new issues found.

Reviewed changes — The latest commit aligns the type system with the runtime string-injection restriction.

• Removed string from Wgsl and isWgsl() so plain JS strings no longer type-check as resolvable values, matching the runtime rejection added earlier.
• Clarified the scoped string-identifer path in ResolutionCtx.resolve() with an inline example showing how identifier snippets carry their concrete schema.

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[iwoplaza]

👏👏👏