* fix(plugin-sdk): remove relative extension boundary escapes
* Gate new plugin-sdk subpaths on host version
* Add changelog entry for #51939
* Fix local staging for plugin-sdk host version gate
* Raise host floor for line and googlechat plugins
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Co-authored-by: Tak Hoffman <781889+Takhoffman@users.noreply.github.com>
Replace "seam" with clearer terms throughout:
- "surface" for public API/extension boundaries
- "boundary" for plugin/module interfaces
- "interface" for runtime connection points
- "hook" for test injection points
- "palette" for the lobster palette reference
Also delete experiments/acp-pluginification-architecture-plan.md
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>