arch: Unified numeric validation layer for NaN/Infinity handling

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Overview

Multiple issues relate to inconsistent handling of NaN, Infinity, and invalid numeric values across the codebase. This tracking issue proposes a unified validation layer.

Related Issues

• OptimizedNodeBridge should guard against negative/NaN timeoutMs #114 - OptimizedNodeBridge should guard against negative/NaN timeoutMs
• Python bridge should disallow NaN/Infinity in JSON responses #95 - Python bridge should disallow NaN/Infinity in JSON responses
• Reject NaN/Infinity in JS arguments to avoid silent conversion #93 - Reject NaN/Infinity in JS arguments to avoid silent conversion
• Bridge timeoutMs should be validated to avoid NaN/negative timeouts #87 - Bridge timeoutMs should be validated to avoid NaN/negative timeouts
• JSON fallback should handle NaN/NaT explicitly #45 - JSON fallback should handle NaN/NaT explicitly

Proposed Architecture

1. Configuration Validation (at construction)

function validatePositiveNumber(value: number, name: string): number {
  if (!Number.isFinite(value) || value <= 0) {
    throw new RangeError(`${name} must be a positive finite number, got: ${value}`);
  }
  return value;
}

2. Argument Validation (before serialization)

function validateSerializable(value: unknown): void {
  if (typeof value === 'number' && !Number.isFinite(value)) {
    throw new BridgeProtocolError(`Cannot serialize ${value} - NaN/Infinity not supported`);
  }
}

3. Response Validation (during deserialization)

• Python bridge rejects NaN/Infinity in JSON responses
• JS codec validates numeric values on decode

Acceptance Criteria

• All bridge constructors validate numeric options (timeoutMs, maxLineLength, etc.)
• BridgeCore.send() validates arguments before serialization
• Python bridge returns explicit error for non-finite numbers
• Codec rejects NaN/Infinity during decode
• All 5 related issues can be closed

Scope

This fix touches:

• src/runtime/node.ts - constructor validation
• src/runtime/bridge-core.ts - argument validation
• runtime/python_bridge.py - response validation
• src/utils/codec.ts - decode validation

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Superseded by #149

This issue is addressed by the unified BoundedContext abstraction proposed in #149.

The numeric validation concerns here will be implemented via:

• validateNumeric(value, name) - validates finite numbers
• validatePositive(value, name) - validates positive numbers
• validateInput() override for argument validation

These are built-in helpers in the BoundedContext base class that all bridges will inherit.

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Resolved by PR #150 (BoundedContext implementation).

The unified numeric validation layer is now available:

• validators.ts: isFiniteNumber, assertFiniteNumber, assertPositive, containsSpecialFloat, assertNoSpecialFloats
• BoundedContext: validateNumeric(), validatePositive() methods

Verified by test suite in PR #151.