docs: reorganize project structure and add Gitea platform context

This commit implements a comprehensive reorganization of project documentation
and adds explicit Gitea platform context throughout the project.

## Documentation Reorganization

### File Moves (Content Preserved)
- Moved CURSOR_WINDOWS_SETUP.md to kb/_guides/ for better organization
- Moved docs/PHASE-UPDATES/ to kb/_guides/PROJECT-SETUP-GUIDE/:
  - COMPLETE-SYSTEM-REPLICATION-GUIDE.md
  - PHASE-0-GITEA-UPDATES.md
  - README.md
- Added new file: kb/_guides/PROJECT-SETUP-GUIDE/PHASE-1-PLAN.md

**Reason**: Consolidate project setup and configuration guides into the
knowledge base structure for better discoverability and organization.

### New Phase Documentation Structure
Created tendril/phases/ directory with structured phase documentation:
- phase-00-foundation/: blueprint, changelog, decisions, tasks
- phase-01-testing-validation/: blueprint, changelog, decisions, tasks

**Reason**: Establish consistent phase documentation structure following
project guidelines for phase management and tracking.

## Gitea Platform Context Integration

### .cursorrules Updates
- Added comprehensive Gitea platform context section
- Added Gitea documentation references for workflows and platform questions
- Added platform terminology guidelines (Gitea vs GitHub)
- Added references to docs/GITEA/ documentation throughout rules

**Reason**: Ensure all AI agents and contributors use correct Gitea terminology
and have clear guidance on where to find Gitea-specific documentation.

### Documentation Path Updates
- CONTRIBUTING.md: Updated CURSOR_WINDOWS_SETUP.md path reference
- docs/AGENT-GUIDELINES.md: Updated path references to moved documentation
- PROJECT_STATUS.md: Updated comment to mention Gitea Actions

**Reason**: Maintain link integrity after file reorganization and ensure
documentation references point to correct locations.

## Impact and Benefits

1. **Better Organization**: Documentation is now organized in logical
   structures (kb/ for knowledge base, tendril/phases/ for phase docs)

2. **Clear Platform Context**: Explicit Gitea platform references prevent
   confusion with GitHub terminology and provide clear documentation paths

3. **Consistent Structure**: Phase documentation follows standardized format
   (blueprint, changelog, decisions, tasks) for easier maintenance

4. **Improved Discoverability**: Guides consolidated in kb/_guides/ make it
   easier to find setup and configuration information

All file moves preserve content - no information was lost in this reorganization.

PROJECT_STATUS.md

@@ -508,7 +508,7 @@ The extension is being mirrored to GitHub for Zed marketplace publication for th
 
 # Keep in sync:
 git push --mirror https://github.com/your-username/tendril.git
-# Or use GitHub Actions for automatic syncing
+# Or use Gitea Actions (or GitHub Actions) for automatic syncing
 ```
 
 ### Marketplace Publication