Share padded decoding across CDP response shapes and cache fingerprints,
and count binary WebSocket bytes without allocating a decoded buffer.
Preserve HAR canonical pad bits and validate before allocation.
Replace repeated alphabet quartets in canonical schemas with separate
alphabet, padding and fixed-width length assertions. Cover near-32MiB
encodings under ordinary, Unicode and Unicode-set modes, plus complete
4MiB CLI and MCP retained-evidence export workflows.
Fixes#5253