fix(web_core): keep Record props as data in ResolveA2uiProp

[josemontespg]

Summary

ResolveA2uiProp turns every prop whose type matches ActionLike into a () => Promise<void> thunk. Since #2859 added V1Action to ActionLike, whose function-call variant infers as the weak type {functionCall?: any}, every object type matches it, so props declared as z.record(z.unknown()) (or any Record<string, ...>) now resolve to an action thunk instead of their data type. The runtime binder is unaffected (it reads the zod schema), so this is a type-only regression, but it breaks tsc for catalogs that read such props, for example the iframe and MCP catalogs in #2797 and #2799.

Object types with a string index signature now resolve as data, as before #2859. Props shaped like an action ({event: ...}, {functionCall: ...}, V1Action) still resolve to the thunk.

Changes

• typescript/web_core/src/resolution/generic-binder.ts: add HasStringIndex<T> and check it inside the ActionLike branch of ResolveA2uiProp before producing the thunk type.
• typescript/web_core/CHANGELOG.md: Unreleased entry.

Verification

• yarn --cwd typescript/web_core test (842 tests) and ./scripts/fix_format.sh --check pass locally.
• The iframe and MCP catalog packages of the stack above typecheck again with this change.

[gemini-code-assist]

Code Review

This pull request introduces a new helper type HasStringIndex in typescript/web_core/src/resolution/generic-binder.ts to identify object types with a string index signature (such as Record<string, unknown>). It also updates the ResolveA2uiProp type utility to handle these types separately from ActionLike types, resolving them to Exclude<T, DynamicTypes> instead of callable functions. There are no review comments, so I have no feedback to provide.