feat(commands): add /memory:validate diagnostic command

Comprehensive validation command that tests:
- Core library imports (capture, recall, sync services)
- Git repository and notes accessibility
- Index health and consistency
- All 5 hook entry points (syntax validation)
- Hook handler imports (stop, posttooluse, precompact)
- Capture pipeline (creates test memory)
- Recall pipeline (semantic and text search)

Options:
- --verbose: Show detailed output
- --fix: Repair index, sync after capture for accurate testing

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

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

Author: zircote

.env.example

@@ -42,3 +42,8 @@
 # Override XDG data home (affects default data directory)
 # Default: ~/.local/share
 # XDG_DATA_HOME=~/.local/share
+#
+# =============================================================================
+# HuggingFace tokenizer parallelism warnings (System)
+# =============================================================================
+# TOKENIZERS_PARALLELISM=false