docs: release v4.6.2 - documentation optimization and /memory:load refinement

### Documentation Optimization

**Optimized `/memory:load` Command Specification**:
- Reduced documentation from 273 to 240 lines (12% reduction)
- Merged redundant sections for better information flow
- Removed unnecessary internal implementation details
- Simplified usage examples while preserving clarity
- Maintained all critical information (parameters, workflow, JSON structure)

### Documentation Updates

**CHANGELOG.md**:
- Added v4.6.2 release entry with documentation improvements

**COMMAND_SPEC.md**:
- Updated `/memory:load` specification to match actual implementation
- Corrected syntax: `[--tool gemini|qwen]` instead of outdated `[--agent] [--json]` flags
- Added agent-driven execution details

**GETTING_STARTED.md**:
- Added "Quick Context Loading for Specific Tasks" section
- Positioned between "Full Project Index Rebuild" and "Incremental Related Module Updates"
- Includes practical examples and use case guidance

**README.md**:
- Updated version badge to v4.6.2
- Updated latest release description

**COMMAND_REFERENCE.md**:
- Added `/memory:load` command reference entry

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

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

COMMAND_REFERENCE.md

@@ -127,6 +127,7 @@ Commands for managing individual tasks within a workflow session.
 | Command | Description |
 |---|---|
 | `/memory:update-full` | Complete project-wide CLAUDE.md documentation update. |
+| `/memory:load` | Quickly load key project context into memory based on a task description. |
 | `/memory:update-related` | Context-aware CLAUDE.md documentation updates based on recent changes. |
 | `/version` | Display version information and check for updates. |
 | `/enhance-prompt` | Context-aware prompt enhancement using session memory and codebase analysis. |