docs: apply eng review fixes - slate-300 context rule, annotated audit, visual smoke checklist

docs/superpowers/plans/2026-04-19-ui-uniformity.md

@@ -26,11 +26,14 @@ The design tokens already exist in `frontend/tailwind.config.ts`. Use these and
 
 **Replace these hardcoded classes with the tokens above:**
 - `text-slate-100`, `text-slate-200` → `text-secondary` (secondary text)
-- `text-slate-300` → `text-secondary` (secondary text, slightly darker)
+- `text-slate-300` in **label/secondary text context** → `text-secondary`
+- `text-slate-300` in **placeholder/disabled/hint context** → `text-muted` ⚠️ check context first
 - `text-slate-400`, `text-slate-500` → `text-muted` (muted/hint)
 - `text-slate-700` (on light bg) → keep as-is (inverted context)
 - `text-white` on headings → keep (page titles only)
 
+> **⚠️ slate-300 context rule:** `text-slate-300` serves two purposes. If it's on a label, heading, or value display → use `text-secondary`. If it's on placeholder text, a disabled input, or a loading skeleton → use `text-muted`. When in doubt, check whether the element is interactive/disabled.
+
 **Font weight standard:**
 - Page titles (main heading per page): `text-2xl font-black` or `text-3xl font-black`
 - Section labels: `text-xs font-black text-muted`
@@ -74,6 +77,10 @@ cd frontend && grep -rn \
 echo "Lines found: $(wc -l < ../docs/superpowers/plans/ui-uniformity-audit.txt)"
 ```
 
+**Then manually annotate `ui-uniformity-audit.txt` for each `text-slate-300` line:**
+Add a comment at the end of the line: `# LABEL` (use text-secondary) or `# PLACEHOLDER` (use text-muted).
+This takes 5 minutes and prevents contrast regressions in disabled form fields.
+
 Commit:
 ```bash
 git add docs/superpowers/plans/ui-uniformity-audit.txt docs/superpowers/plans/2026-04-19-ui-uniformity.md
@@ -270,9 +277,20 @@ git commit -m "style: step 11 - uniform text tokens in remaining components"
 ```bash
 cd frontend && npm run build 2>&1 | tail -10
 cd frontend && npm run test -- --run 2>&1 | tail -5
-# Manually verify: login page, main page, inventory, admin, at least one modal
+# Must: 0 build errors, 291 tests passing
 ```
 
+**Visual smoke checklist (open the app, check each item):**
+- [ ] Login page: disabled inputs look visibly dimmer than active inputs
+- [ ] Login page: placeholder text is lighter than typed text
+- [ ] Main page (scanner): section labels are clearly smaller/lighter than page title
+- [ ] Inventory page: table row text reads at consistent weight/color throughout
+- [ ] Admin page: error messages appear in red, not muted gray
+- [ ] Any modal (e.g., Create User): modal title is clearly the largest text inside it
+- [ ] `text-muted` elements are visibly lighter than `text-secondary` elements anywhere on same page
+
+All 7 must pass visually before marking this step complete.
+
 Update this file: mark all steps done. Then update `dev_docs/SESSION_STATE.md`.
 
 Commit: