specTypeSchema()/isSpecType() now also cover the OAuth/OpenID types from
shared/auth.ts (OAuthTokens, OAuthMetadata, OAuthClientMetadata, etc.),
addressing the standalone-validation use noted in #1680 for auth
implementers.

…cTypeSchema()/isSpecType()

- Explicit auth-schema allowlist (excludes SafeUrl/OptionalSafeUrl/IdJagTokenExchangeResponse helpers)
- Guard predicate types value as schema input (z.input), not output, since safeParse only proves input shape
- SchemaRecord typed as StandardSchemaV1<In, Out> so validate() output is the spec type
- JSDoc/migration examples await validate() (Result | Promise<Result>); drop stale setCustom* refs

…-checked @example snippets

- Replace import-* derivation with explicit SPEC_SCHEMA_KEYS tuple (150 entries
  with a matching public type in types.ts). Excludes internal helper schemas
  (ListChangedOptionsBase, BaseRequestParams, NotificationsParams,
  Client/ServerTasksCapability, ResourceTemplate name mismatch).
- Add test asserting internals are not in SpecTypeName.
- Bump changeset patch -> minor (5 new public exports).
- Move @example code into specTypeSchema.examples.ts and source via
  sync:snippets, per repo convention.

…ture

…emas with defaults

The previous 'narrows the value type' test asserted against SpecTypes['Implementation']
(the output type), which only passed because Implementation has no defaults. Clarified
that case and added a CallToolResult case that proves the documented input-type narrowing:
content is optional in the narrowed type, and the narrowed type is not CallToolResult.

specTypeSchemas.X is typed as StandardSchemaV1, which only exposes
['~standard'].validate. The .parse() method exists at runtime (Zod) but
is not on the public type, so the parenthetical produced a TS error if
followed.

ResourceTemplate is a first-class spec type with a public type export
(ResourceTemplateType). It was excluded under the assumption that the
name collides with the server package's ResourceTemplate class, but
isSpecType.ResourceTemplate is a record property, not a top-level
export, so no collision occurs. Including it makes the migration docs'
'every named type in the MCP spec' claim accurate.

Corrected the allowlist comment (ResourceTemplate is not an internal
helper) and added type-level and runtime tests.

…ype describe block

JSONValueSchema/JSONObjectSchema/JSONArraySchema were typed as
z.ZodType<T> (output only). Zod v4's ZodType<O, I> defaults I to
unknown, so z.input<typeof JSONValueSchema> was unknown and
isSpecType.JSONValue was (v: unknown) => v is unknown, a no-op
predicate. Annotating as z.ZodType<T, T> fixes the input type at the
source (these schemas have no defaults/transforms, so input equals
output). Test asserts the narrowing.

…arg function form

Replaces the Record-of-predicates exports with two generic functions:
isSpecType('TypeName', value) and specTypeSchema('TypeName').

Drops the register() helper, the per-key closure creation (161 closures
at module init), the SchemaRecord/GuardRecord types, and both
Object.freeze(...) as unknown as casts. The single remaining cast is a
narrow Record<SpecTypeName, z.ZodType> at construction so indexing by
SpecTypeName is non-undefined under noUncheckedIndexedAccess.

Trade-off: arr.filter needs an arrow wrapper (mixed.filter(v =>
isSpecType('ContentBlock', v))). TypeScript's inferred type predicates
still narrow the result to ContentBlock[].