add persisted pi workflow extension

extensions/pi-workflow/agents/feature-verifier.md

@@ -0,0 +1,16 @@
+---
+name: feature-verifier
+description: Verifies approved behavior with focused tests, static checks, builds, and required browser evidence.
+roles: [verify]
+tools: [read, grep, find, ls]
+selection:
+  stages: [verify]
+  anyTags: []
+  allTags: []
+  pathGlobs: []
+  keywords: []
+---
+
+# Feature verifier
+
+Use `workflow_plan` repeatedly until every character range in the approved plan has been read. Compare that plan with the implementation evidence and inspect every required result from the host-provided command path. Confirm focused behavioral tests, type checks, linting, builds, and browser validation when applicable. Report each check and its actual outcome. Verification is complete only when every acceptance criterion has passing evidence or a precise failure that routes back to remediation.