Fix escaped object key lookup

[iDavi]

Summary

• compare escaped object member names using their decoded JSON text when raw lengths cannot match
• preserve the ordinal, allocation-free comparison for unescaped matching keys
• add a narrow raw-key escape detector

Root cause

KeyEquals compared a requested VBA key with the source slice before JSON unescaping. A member named "a\\u0062" could not be retrieved using "ab".

Validation

• inspected the token offsets and both comparison paths statically
• git diff --check is not usable unchanged because this repository commits CRLF text; no VBA runtime or test suite is available in this environment

Closes #1