fix(core): deserialize numeric members to number when the reviver is active

[RasengunShotaro]

Issue

#8246

Description

needsReviver returns true when a response schema contains a bigInteger, bigDecimal or document member, which enables the JSON.parse reviver for the whole body. jsonReviver then rewrites every numeric literal that does not round-trip (1.0, 0.0, 1e3, anything past Number.MAX_SAFE_INTEGER), including literals that belong to plain numeric members, and the shape deserializer passed those values through unchanged.

The result is that a member whose generated type is number can deserialize to a NumericValue. It fails silently: typeof result.score becomes "object" and result.score + 1 evaluates to the string "1.01" instead of 2. TypeScript cannot catch it, because the generated type says score?: number, so a typeof x === "number" guard looks redundant and is a candidate for removal.

This affects any client whose response shape contains a document member. It was found on bedrock-agent-runtime Retrieve, where RetrievalResultMetadata is Map<String, Document>: the knowledge base returns page numbers as 22.0 inside metadata, and the relevance score in the same response was corrupted as collateral for exact 1.0 / 0.0 values.

Numeric members now coerce a revived NumericValue or BigInt back to number, which matches the generated types and the behaviour before @aws-sdk/core@3.977.0. Documents keep the revived representation, which is unchanged and appears intended.

Applied to both codecs (JsonShapeDeserializer and JsonShapeDeserializer2) so v1/v2 equivalence is preserved.

Testing

Added a test to each codec spec asserting that a numeric member deserializes to number while the reviver is active (1.0 → 1, 0.0 → 0, 1e3 → 1000). Both fail without the change:

× JsonShapeDeserializer > deserializes numeric members to number when the reviver is active
  → expected { scalar: NumericValue{ …(2) } } to deeply equal { scalar: 1 }

Full protocols suite after the change: 32 files, 516 passed, 2 skipped.

One existing expectation is updated. In JsonShapeDeserializer2.spec.ts, fractional exponent with many digits does not throw in reviver asserted that {"scalar": 1.123456789012345678E16} stays a NumericValue. scalar is a numeric member, and JSON.parse produced 11234567890123456 for that input before the reviver existed, so the expectation is changed to that value. The purpose of the test — that the reviver does not throw — is unaffected, and the neighbouring v1/v2 equivalence cases still pass.

I could not run the repo's full yarn install locally, so verification was scoped to packages-internal/core/src/submodules/protocols with dependencies installed from npm.

Checklist

• If the PR is a feature, add integration tests (*.integ.spec.ts) or E2E tests.
  • It's not a feature.
• My E2E tests are resilient to concurrent i/o.
  • I didn't write any E2E tests.
• I added access level annotations e.g. @public, @internal tags and enabled doc generation on the package. Remember that access level annotations go below the description, not above.
  • I didn't add any public functions.
• Streams - how do they work?? My WebStream readers/locks are properly lifecycled. Node.js stream backpressure is handled. Error handling.
  • No streams here.

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