refactor: rename tilde api with dollar - #4086

Reviewed changes — renames ~hooks to $hooks and ~resolvers to $resolvers across plugin config types, runtime code, and documentation, with @deprecated annotations on the old keys for backward compatibility.

• Add $hooks and $resolvers to PluginBaseConfig and Plugin.Resolvers types — new fields in packages/shared/src/plugins/types.ts with @deprecated on ~hooks and ~resolvers
• Update all resolver access sites — every toAst function and validator resolver across typescript, zod (mini/v3/v4), valibot, and pydantic now checks $resolvers first, falling back to ~resolvers
• Update PluginInstance hook reading — buildEventHooks, getHooks, and isOperationKind in packages/shared/src/plugins/shared/utils/instance.ts try $hooks first
• Update plugin export types — Required<...>['$resolvers'] in index.ts for both openapi-ts and openapi-python
• Update documentation — parser, resolvers, custom plugin, and SDK docs reference $hooks/$resolvers
• Add changesets — patch for @hey-api/openapi-ts and @hey-api/shared

ℹ️ Nitpicks

• packages/shared/src/plugins/shared/utils/__tests__/instance.test.ts still uses '~hooks' in test config — worth migrating to $hooks (and/or adding coverage for the $hooks path) in a follow-up.

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