Cache key generation should disambiguate input types to avoid collisions

[bbopen]

Summary

globalCache.generateKey hashes raw string values and JSON.stringify for non-strings. This can produce collisions between different types (e.g., string "1" vs number 1, string "null" vs null).

Failure mode

• generateKey('x', '1') and generateKey('x', 1) hash the same input sequence.
• generateKey('x', 'null') and generateKey('x', null) collide.
• Collisions can return cached results for the wrong inputs.

Evidence

• src/utils/cache.ts generateKey uses hash.update(input) for strings and hash.update(JSON.stringify(input)) for other primitives, with null/undefined also mapped to 'null'.

Proposed fix

• Prefix each input with a type tag (e.g., str:, num:, bool:, null:) before hashing.
• Alternatively, use a stable JSON encoder that preserves types for primitives.

Acceptance criteria

• Distinct primitive inputs (string vs number vs null) produce distinct keys.
• Add tests verifying no collisions for 1, "1", true, "true", null, "null".