Convert an unknown legacy plugin wrapper such as
{kind: 'plugin', plugin: 'acme'} into {kind: 'plugin:acme'}, retaining the
complete plugin name after one prefix. Keep the existing explicit
first-party producer renames and preserve all non-identity metadata.
A direct source already records its producer in kind. Reclassifying
unknown direct kinds into plugin:source:<name> needlessly changes that
attribution and forces plugin consumers to adopt new identifiers even
though V4 accepts their existing representation. Return every valid
direct source unchanged, including already-prefixed names. Remove the
obsolete direct-kind table and two-category identity helper rather than
adding collision classification or another mapping layer.
Update the source conversion examples, codec/restore regressions, and
native fixture producers together. Refresh only the owning Python
advanced scenario's unshipped V4 outputs; preserve historical V0-V3
recordings and their generation selection. Event names, content tags,
and ToolSchema migration remain separate concerns.
Refs #2692
Tianyi Cui
d5a109c60f