Workflow 2.6.2

Reuse small unchanged JSON history payloads on the default Eloquent model, avoiding repeated decoding during reads.

• Cache entries are bounded to 4 KiB of JSON and 128 recursive values. Larger payloads continue through the ordinary cast, with no new data or admission limit.
• Configured models, custom casts and JSON decoders, payload mutation, raw stored bytes and serialization retain their behavior.
• No database migration or service protocol change is required. Restart long-running workers after upgrading to load the new code.

This patch does not enable retained workflow execution or establish a production performance gain. The broader warm-execution work remains open in #748.

Changes: #848 and #849. Exact release source: 67833a7938b65e8ec663b4a63b25b4ac1b0beeef.