Fixes #18: Update README & AGENTS.md documentation

- README: Add Equipment System feature, Code Quality, Performance,
  Memory Management, Testing, Development Commands, and Tech Stack sections
- AGENTS.md: Update source tree with CSS modules, equipment constants,
  renderUtils, settings consolidation; add development commands,
  performance optimizations, memory management notes, validator factory;
  update file reference table

Based on PRs: #1 #3 #6 #8 #10 #12 #14 #17

README.md

@@ -41,6 +41,7 @@ Moving on to developing the Marinara Engine frontend, the extension will now be
 - **🎭 Floating Thought Bubbles**: Optional thought bubbles positioned next to character avatars in chat
 - **🎲 Classic RPG Stats**: STR, DEX, CON, INT, WIS, CHA attributes with dice roll support
 - **📦 Advanced Inventory System**: Multi-location storage (On Person, Stored locations, Assets) with v2 format
+- **⚔️ Equipment System**: 19 equipment slots (Helmet, Necklace, Body Armor, Gloves, Pants, Shoes, 10 Rings, 3 Accessories) with slot-type validation, stat bonuses (+99 max), and automatic slot assignment
 - **🎯 Character Stats**: Track health, energy, or any custom stats for each present character with color interpolation
 - **📜 Immersive HTML**: Enhance the immersion by including creative HTML/CSS/JS elements in your roleplay
 - **➡️ Plot Progression**: Progress the plot with randomized events or natural progression with a click of a button
@@ -226,6 +227,49 @@ Choose from 6 beautiful themes:
 
 If you ever have an awesome idea to do your own SillyTavern extension, don't.
 
+### Code Quality
+
+- **index.js refactored**: 1567 lines → 456 lines (73% reduction) through modular extraction
+- **CSS modularized**: 28 logical modules in `src/styles/` with automated build script
+- **Settings consolidation**: `config.js` as single source of truth — state.js imports from it (~300 lines eliminated)
+- **Validator factory pattern**: `createStringValidator()` unifies `sanitizeLocationName`/`sanitizeItemName`
+- **Prompt builder refactored**: `getCharacterCardsInfo` extracted into focused helper functions
+- **Error visibility**: `jsonRepair.js` silent failures now log to `console.debug`
+
+### Performance
+
+- **Rendering**: `requestAnimationFrame` batching in `rerenderRpgState()`, `updateIfChanged()` cache in `renderUtils.js`, CSS `content-visibility: auto` on inventory/equipment containers
+- **Parser**: Regex pre-compilation (~64 patterns in `parser.js` + `jsonRepair.js` as module-level constants), format detection caching (`lastDetectedFormat` with 3-hit threshold), `clearFormatCache()` for invalidation
+- **CSS**: Minification support (`--minify` flag in build script), extended CSS custom properties, theme refactoring (379 → ~220 lines), `style.css` reduced from 305.4 KB → 293.9 KB (3.8%), minified build adds ~50%+ further reduction
+
+### Memory Management
+
+- **`clearDomCache()`**: Invalidates jQuery object cache on panel rebuild to prevent stale references
+- **Event tracking**: All `on()`/`once()` handlers tracked for cleanup via `unregisterAllEvents()`
+- **`clearDebugLogs()`**: Called on `CHAT_CHANGED` to prevent unbounded debug log growth
+
+### Testing
+
+- **78 tests passing** (up from 54) using Jest with Babel ESM support
+- ESM compatibility via `babel.config.json` + `jest.config.cjs` transform configuration
+- Security-focused test suite (`security.test.js`, 24 tests)
+
+### Development Commands
+
+```bash
+npm run build:css          # Concatenate CSS modules
+npm run build:css:min      # Minified production build
+npm test                   # Run Jest test suite
+npm run validate_locale    # Watch mode translation validation
+npm run validate_locale_once
+```
+
+### Tech Stack
+
+- `"type": "module"` — ES modules throughout
+- Jest + Babel for testing with full ESM support
+- Modular CSS build pipeline with minification support
+
 ## 🐛 Troubleshooting
 
 ### Extension doesn't appear