* fix(plugin-sdk): back every workspace facade export with a real src facade
packages/plugin-sdk declared 59 export subpaths but only 24 had src facade
files; the other 35 defaults pointed at nonexistent ./src/<name>.ts targets
that typecheck (types resolve via boundary dist) but fail runtime resolution.
Create the 35 missing facades (each mirrors the sibling 3-line re-export of
the core src/plugin-sdk entrypoint; all verified live, none retired), and
extend scripts/sync-plugin-sdk-exports.mts to own the facade package too:
exports are regenerated from the src directory, every facade must name a
canonical SDK entrypoint, and --check fails on dangling keys or orphan
facades. The check-changed Plugin SDK surface lane now also triggers on
packages/plugin-sdk/** so the guard actually runs when the map changes.
* fix(plugin-sdk): validate facades before any exports write
ClawSweeper P2: write mode reported a stale facade but still exited 0,
after syncRootPackageExports had already rewritten the root manifest.
Hoist facade validation ahead of all writes and exit nonzero in both
modes; an invalid facade now fails closed with no partial manifest
update (proven: hash-identical manifests plus exit 1 in write mode).
Peter Steinberger