Fix slice offsets outside the signed 32-bit range

[Huzaifa-Asif]

Fixes #315.

Buffer.prototype.slice currently converts start and end with ~~, which wraps large offsets to signed 32-bit values. For example, Buffer.from([1, 2, 3]).slice(1, 2 ** 32) returns an empty buffer instead of [2, 3].

Replace those two coercions with Math.trunc, preserving the existing bounds adjustment and shared-memory view. Regression coverage includes large positive and negative offsets, fractional and non-finite values, string/object coercion, and nested slice aliasing. The new tests produce 22 failing assertions before the fix; all 60 focused slice assertions pass afterward.

Verification

• all 60 focused slice assertions pass locally on Node 24
• full npm test: 1,048,618 assertions passed during preparation on Node 18, 20, 22, and 24
• JavaScript Standard Style and git diff --check pass
• 72,200 native-Buffer comparison cases had zero mismatches after the fix
• browser bundles build, but real-browser execution was blocked by the preparation environment and remains unverified
• the CI Node 16 job was not run locally

AI assistance disclosure

OpenAI Codex assisted with investigation, implementation, tests, review, and drafting this description. No human-review attestation is made.