feat: add MemPalace Claude Code plugin with hooks and instructions

- Introduced README.md for plugin overview and installation instructions.
- Added hooks configuration in hooks.json for auto-save and pre-compact functionality.
- Implemented stop and pre-compact hooks in bash scripts for memory management.
- Created marketplace.json and plugin.json for plugin metadata and versioning.
- Developed skills and instructions for help, init, mine, search, and status functionalities.
- Added CLI commands for executing hooks and displaying skill instructions.
- Implemented hooks_cli.py for handling hook logic and JSON input/output.
- Enhanced instruction files for user guidance on setup and usage.
- Updated .gitignore to exclude additional files.
- Created GitHub Actions workflow for syncing plugin version on push.

.claude-plugin/hooks/mempal-precompact-hook.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+# MemPalace PreCompact Hook — thin wrapper calling Python CLI
+# All logic lives in mempalace.hooks_cli for cross-harness extensibility
+INPUT=$(cat)
+echo "$INPUT" | python3 -m mempalace hook run --hook precompact --harness claude-code