fix(phase6): Resolve critical instruction contradictions and add validation

## Critical Issues Fixed

### Issue #1: Indentation Contradictions (CRITICAL)
- **wpcs-php.instructions.md**: Fixed line 379 contradiction
  - Changed from "Use 4 spaces for indentation, no tabs"
  - To: "Use tabs for indentation (WordPress PHP standard)"
  - Now consistent with line 24 which correctly states "tabs"
- **wpcs-javascript.instructions.md**: Clarified JS indentation rules
  - Line 131: Added context "tabs for vanilla JavaScript (WordPress core standard)"
  - Line 132: Added "For React/JSX files, use 2 spaces to align with @wordpress/scripts"
  - Line 562: Clarified "2 spaces for React/JSX files (Gutenberg standard), tabs for vanilla JS"
  - Resolves contradiction between tabs (line 131) and 2 spaces (line 561)

### Issue #3: Placeholder Preservation Checklist (CRITICAL)
- **scaffold-extensions.instructions.md**: Added comprehensive validation section
  - New "Mustache Placeholder Preservation Checklist" with 6 subsections
  - Core Placeholders checklist (namespace, slug, textdomain, name, etc.)
  - Template Files checklist (patterns, templates, blocks)
  - Common Hard-coding Mistakes with BAD vs GOOD examples
  - 5-step Validation procedure including mustache scanning
  - Documentation requirements for new placeholders
  - Risk prevention identifying high-risk files

## Impact

### Before:
- AI agents received contradictory guidance on indentation
- No explicit validation checklist for mustache placeholder preservation
- Risk of hard-coded values breaking scaffold generation

### After:
- Clear, consistent indentation standards (PHP: tabs, React: 2 spaces, vanilla JS: tabs)
- Comprehensive checklist prevents mustache placeholder violations
- Explicit validation steps ensure scaffold integrity

## Validation

✅ Instructions now consistent across all WPCS files
✅ Placeholder preservation explicitly documented with examples
✅ High-risk files identified for extra caution
✅ 5-step validation procedure added

## Files Modified

- .github/instructions/wpcs-php.instructions.md (1 line corrected)
- .github/instructions/wpcs-javascript.instructions.md (3 sections clarified)
- .github/instructions/scaffold-extensions.instructions.md (106 lines added)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: ashleyshaw

.github/instructions/scaffold-extensions.instructions.md

@@ -374,8 +374,108 @@ Do not include any production opinions; keep everything clearly marked as exampl
 - Add new binding placeholder: `{{binding_example}}` documented in `scripts/mustache-variables-registry.json`.
 - New template part placeholder: `templates/parts/{{slug}}-cta.php` with namespaced CSS class `{{namespace}}-cta`.
 
-## Validation
+## Mustache Placeholder Preservation Checklist
 
-- Run `node scripts/scan-mustache-variables.js` after adding placeholders.
-- Run `npm run lint` and `composer lint` to ensure scaffolding code remains valid.
-- Generate a sample plugin to confirm no raw placeholders or missing files remain.
+Before committing any changes to scaffold files, ensure:
+
+### ✅ Core Placeholders Never Hard-coded
+
+- [ ] `{{namespace}}` - Used for PHP namespaces, block registration, CSS classes
+- [ ] `{{slug}}` - Used for post types, taxonomies, file/folder names, URLs
+- [ ] `{{textdomain}}` - Used for all `__()`, `_e()`, `esc_html__()` translation functions
+- [ ] `{{name}}` - Used for user-facing display names
+- [ ] `{{name_plural}}`, `{{name_singular}}` - Used for CPT labels
+- [ ] `{{author}}`, `{{author_uri}}`, `{{version}}`, `{{license}}` - Used in plugin headers
+
+### ✅ Template Files Preserve Placeholders
+
+- [ ] **Patterns** (`patterns/*.php`): All CSS classes use `{{namespace}}` and `{{slug}}`
+- [ ] **Templates** (`templates/*.html`): Block references use `{{namespace}}/{{slug}}-*`
+- [ ] **Template Parts** (`template-parts/*.html`): Taxonomy references use `{{slug}}_category`
+- [ ] **Block render.php**: ACF field names use `{{namespace}}_field_name` format
+- [ ] **Block edit.js**: CSS classes follow `wp-block-{{namespace}}-{{slug}}-*` pattern
+- [ ] **Block view.js**: Selectors dynamically construct class names from block attributes
+
+### ✅ Common Hard-coding Mistakes to Avoid
+
+❌ **DON'T DO THIS:**
+```php
+// BAD: Hard-coded namespace
+namespace example_plugin\classes;
+$field = get_field( 'example_plugin_subtitle' );
+
+// BAD: Hard-coded CSS class
+<div className="wp-block-example_plugin-example_plugin-card">
+
+// BAD: Hard-coded text domain
+__( 'View All Tours', 'example-plugin' )
+```
+
+✅ **DO THIS:**
+```php
+// GOOD: Mustache placeholders
+namespace {{namespace|lowerCase}}\classes;
+$field = get_field( '{{namespace}}_subtitle' );
+
+// GOOD: Dynamic placeholders
+<div className="wp-block-{{namespace}}-{{slug}}-card">
+
+// GOOD: Template placeholder
+__( 'View All {{name_plural}}', '{{textdomain}}' )
+```
+
+### ✅ Validation Steps
+
+After making changes to scaffold templates:
+
+1. **Scan for new variables:**
+   ```bash
+   node scripts/scan-mustache-variables.js
+   ```
+
+2. **Validate registry integrity:**
+   ```bash
+   node scripts/validate-mustache-registry.js
+   ```
+
+3. **Run all linting:**
+   ```bash
+   npm run lint
+   composer lint
+   ```
+
+4. **Generate test plugin:**
+   ```bash
+   node scripts/generate-plugin.js --config tests/fixtures/plugin-config.test.json
+   ```
+
+5. **Check generated output has NO unreplaced mustache variables:**
+   ```bash
+   grep -r "{{" generated-plugins/test-plugin/ | grep -v node_modules | grep -v build
+   ```
+   Should return no results (except in comments explaining the system).
+
+### ✅ Documentation Requirements
+
+When adding new placeholders:
+
+- [ ] Add to `scripts/mustache-variables-registry.json` with:
+  - Variable name
+  - Description
+  - Category (namespace, text, meta)
+  - Example value
+  - All files where it's used
+- [ ] Update `docs/GENERATE-PLUGIN.md` if it's user-facing
+- [ ] Add example to this instruction file showing correct usage
+- [ ] Update `.github/agents/generate-plugin.agent.md` if it affects the generator interface
+
+### ✅ Risk Prevention
+
+**HIGH RISK:** These files are most likely to accidentally introduce hard-coded values:
+
+- `src/blocks/*/edit.js` - Block editor components with CSS class strings
+- `src/blocks/*/render.php` - Dynamic block rendering with ACF fields
+- `patterns/*.php` - Block patterns with inline styles and classes
+- `inc/class-*.php` - PHP classes with namespaces and text domains
+
+Always verify these files after editing.

.github/instructions/wpcs-javascript.instructions.md

@@ -128,7 +128,8 @@ Use spaces liberally throughout your code. "When in doubt, space it out."
 
 These rules encourage liberal spacing for improved developer readability. The minification process creates a file that is optimized for browsers to read and process.
 
-- Indentation with tabs.
+- Indentation with tabs for vanilla JavaScript (WordPress core standard).
+- For React/JSX files, use 2 spaces to align with @wordpress/scripts and modern tooling.
 - No whitespace at the end of line or on blank lines.
 - Lines should usually be no longer than 80 characters, and should not exceed 100 (counting tabs as 4 spaces). _This is a "soft" rule, but long lines generally indicate unreadable or disorganized code._
 - `if`/`else`/`for`/`while`/`try` blocks should always use braces, and always go on multiple lines.
@@ -558,7 +559,7 @@ function getKeyCode(keyCode) {
 ## Language & Frameworks
 
 - **ES Version**: ES2020+ with Babel transpilation
-- **Indentation**: 2 spaces (conform to WordPress standards)
+- **Indentation**: 2 spaces for React/JSX files (Gutenberg standard), tabs for vanilla JS (WordPress core standard)
 - **Quotes**: Single quotes (`'`) for strings, template literals for interpolation
 - **Semicolons**: Required at end of statements
 - **Naming**: `camelCase` for variables/functions, `PascalCase` for classes/components

.github/instructions/wpcs-php.instructions.md

@@ -376,7 +376,7 @@ function my_plugin_rest_permission_check() {
 ## PHP Block & Theme Setup Instructions
 
 - Follow WordPress coding standards: <https://developer.wordpress.org/coding-standards/wordpress-coding-standards/php/>
-- Use 4 spaces for indentation, no tabs
+- Use tabs for indentation (WordPress PHP standard)
 
 ## Pattern Registration