Clarify clean validation for stale artifacts

Author: johnml1135

.github/instructions/build.instructions.md

@@ -71,7 +71,7 @@ Re-run the scripted build:
 If the failure persists, check the first error (later ones often cascade) and confirm native Phase 2 succeeds.
 
 ### Stale intermediates
-Prefer re-running `.\build.ps1` first (it performs cleanup needed for this repo). If you must do a hard reset, delete `Output/` and `Obj/`, then run `.\build.ps1` again.
+Prefer `.\build.ps1 -Clean` when switching branches or worktrees, after package or version bumps, when stale `Obj/` or `Output/` artifacts are plausible, or when you need a completely clean validation run. If you must do a harder reset beyond that, delete `Output/` and `Obj/`, then run `.\build.ps1` again.
 
 ## References
 - Traversal order: `FieldWorks.proj`

.github/skills/verify-test/SKILL.md

@@ -18,17 +18,19 @@ You will receive:
 <workflow>
 1. **Select verification steps**
    - Choose the minimal tests or checks that validate acceptance signals.
+    - If stale intermediates or copied outputs could invalidate the result, include a clean validation pass.
 2. **Run verification**
    - Execute builds/tests or manual checks as appropriate.
+    - For FieldWorks, run `./build.ps1 -Clean` before validation when switching branches or worktrees, upgrading package versions, suspecting stale `Obj/` or `Output/` artifacts, or any time you need a fully clean validation baseline.
+    - After the clean step, rerun the normal scripted verification commands such as `./build.ps1`, `./test.ps1`, or the narrow scripted slice you are validating.
 3. **Capture results**
    - Record pass/fail outcomes and any artifacts.
 4. **Report**
    - Summarize verification coverage and gaps.
 </workflow>
 
 <constraints>
-- Prefer repo-standard build/test entry points.
-- Document any skipped verification and why.
+- In FieldWorks, do not rely on incremental validation alone when stale native or managed artifacts are plausible.
 </constraints>
 
 <notes>