Add seed script with 7 trees, markdown rendering, and dark mode docs

- Add comprehensive seed script with 7 troubleshooting decision trees
  - Tier 1: Password Reset, Outlook/Email, VPN, Printer Problems
  - Tier 2: Slow Computer, Network Connectivity
  - Tier 3: File Share Access Problems
- Add markdown rendering with react-markdown package
  - MarkdownContent component for session player and node editor
  - Preview toggle in description fields
- Update documentation to reflect dark mode is complete
- Update all progress tracking docs with recent changes

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

CURRENT-STATE.md

@@ -2,7 +2,7 @@
 
 > **Purpose:** Quick-reference file showing exactly where the project stands.
 > **For Claude Code:** Read this first to understand what's done and what's next.
-> **Last Updated:** January 28, 2026
+> **Last Updated:** January 29, 2026
 
 ---
 
@@ -43,7 +43,12 @@
   - ✅ Visual tree preview with solution indicators
   - ✅ Shared node detection (multiple sources → same target)
   - ✅ Modal with scrollable content, fixed header/footer
-- ⏳ User preferences (dark mode) - NOT YET STARTED
+  - ✅ Markdown preview toggle in description fields
+- ✅ **Markdown Rendering** - Session player and node editor
+  - ✅ `react-markdown` package installed
+  - ✅ `MarkdownContent` component created
+  - ✅ Renders bold, italic, lists, code blocks, headers
+- ✅ User preferences (dark mode) - COMPLETE
 - ⏳ Keyboard shortcuts - NOT YET STARTED
 
 ### Documentation
@@ -61,9 +66,10 @@
 |------|--------|-------|
 | Tree Editor | Functional | Core editing complete, polish ongoing |
 | Tree Editor Validation | Partial | Basic validation working |
-| User Preferences | Not started | Dark/light mode, export format default |
+| User Preferences | **Partial** | Dark/light mode complete, export format default pending |
 | TypeScript strict mode | Warnings exist | tsconfig needs `strict: true` |
-| Starter decision trees | 1 of 5 complete | Need 4 more real trees |
+| Starter decision trees | **7 of 7 complete** | Comprehensive seed script created |
+| Markdown Rendering | **Complete** | Session player + node editor |
 | Deployment | Not started | Railway/Render planned |
 
 ---
@@ -72,9 +78,9 @@
 
 ### Immediate (This Week)
 1. Complete Tree Editor validation (required fields, orphan detection)
-2. Add User Preferences (theme toggle, export format default)
+2. ~~Add User Preferences (theme toggle, export format default)~~ Theme toggle **COMPLETE**, export format pending
 3. Fix TypeScript strict mode warnings
-4. Create remaining 4 starter decision trees
+4. ~~Create remaining 4 starter decision trees~~ **COMPLETE** - 7 trees seeded
 
 ### Soon (Phase 2 Completion)
 - Team management
@@ -189,7 +195,26 @@ pytest
 
 ---
 
-## Recent Changes (Jan 28, 2026)
+## Recent Changes (Jan 29, 2026)
+
+1. **Comprehensive Seed Script** (`backend/scripts/seed_trees.py`):
+   - 7 complete troubleshooting decision trees with 10-20+ nodes each
+   - **Tier 1 (Help Desk)**: Password Reset, Outlook/Email, VPN Connection, Printer Problems
+   - **Tier 2 (Desktop Support)**: Slow Computer, Network Connectivity
+   - **Tier 3 (Systems)**: File Share Access Problems
+   - Real PowerShell commands in action nodes
+   - Professional ticket documentation in solution nodes
+2. **Markdown Rendering** in Session Player and Node Editor:
+   - Installed `react-markdown` package
+   - Created `MarkdownContent` component (`frontend/src/components/ui/MarkdownContent.tsx`)
+   - Updated `TreeNavigationPage.tsx` to render descriptions with markdown
+   - Added markdown preview toggle in `NodeFormAction.tsx` and `NodeFormResolution.tsx`
+   - Supports: bold, italic, lists, code blocks, headers, blockquotes
+3. Updated LESSONS-LEARNED.md with:
+   - httpx installation requirement for seed scripts
+   - Email validation rejecting `.local` TLD (RFC 6761)
+
+## Previous Changes (Jan 28, 2026)
 
 1. Fixed DateTime timezone bugs in all models
 2. Added production logging system
@@ -222,10 +247,17 @@ pytest
 
 *Update this section at the end of each coding session:*
 
-**Last Session (Jan 28, 2026):**
+**Last Session (Jan 29, 2026):**
+- Created comprehensive seed script with 7 troubleshooting trees
+- Added markdown rendering to session player and node editor
+- Installed react-markdown package and created MarkdownContent component
+- Added markdown preview toggle in description fields
+- Fixed httpx and email validation issues (documented in LESSONS-LEARNED.md)
+- Next: User preferences UI, Tree Editor validation polish, deployment
+
+**Previous Session (Jan 28, 2026):**
 - Completed Tree Editor core implementation
 - Fixed modal scroll/overflow issue (content scrolls, header/footer fixed)
 - Added SharedLinksMap for tracking nodes that link to same target
 - Improved NodePicker with type-grouped dropdown
 - Added solution connection indicators in preview
-- Next: Tree Editor validation polish, user preferences UI