Workflow 2.5.29

Reduce repeated payload decoding when constructing timer projections. Each
projection reuses its decoded event payload while preserving exact timestamps,
timer metadata and fresh values on later calls.

This patch includes regression coverage for scheduled, fired and cancelled
timers, partial history models and condition/signal/parallel metadata.

Update the Workflow package to 2.5.29 and restart persistent workers to load
the new code.

See #826 for qualification.