EDN BLOB decode should use exact blob size (avoid trailing bytes)

[delaneyj]

Problem

The EDN decode path for encoded BLOB values currently relies on C-string semantics. That can read past the actual SQLite BLOB payload and include trailing bytes.

Impact

EDN decoding may observe random trailing bytes, causing malformed decode results or parse failures.

Scope

• src/sqlite4clj/impl/encoding.clj

Proposed fix

Decode EDN from the exact SQLite BLOB length:

• Pass payload size into decode-edn
• Slice exactly size bytes from the memory segment
• Build UTF-8 string from that byte slice before edn/read-string

This keeps decoding bounded to the true BLOB content.