docs(plan): close CPU embedding tuning task

Author: GlitterKill

devdocs/superpowers/plans/2026-08-27-cpu-tier-embedding-tuning.md

@@ -977,7 +977,7 @@ git diff --check
 
 Expected: all commands pass; lint has zero errors. Do not run `index.refresh`.
 
-- [ ] **Step 7: Commit documentation and request final review**
+- [x] **Step 7: Commit documentation and request final review**
 
 Stage only the reviewed paths, commit the final preset/evidence/docs, then run
 `@requesting-code-review` against `b5ffb751..HEAD`. Do not merge or push.