feat: add journal submission kits + paper scaffold; restructure package

- init journal <elsevier|ieee|springer>: self-contained, make-buildable kits
  (Springer sn-jnl.cls + bst bundled; reuses project references.bib)
- init paper scaffold: ctexart + Fandol fonts, bib at root, latexdiff highlighted
- move templates/ under mytoolkit/, add info/references, relocate protocols
- migrate mytoolkit skill into submodule; update README/CLAUDE docs

Makefile

@@ -5,12 +5,13 @@ PYTHON ?= python3
 # 手动安装的文件清单（与 bin/commands/self_mgmt.py 中的 _MANUAL_FILES 保持同步）
 MANUAL_FILES := $(COMP_DIR)/_mytoolkit $(COMP_DIR)/mytoolkit.bash
 
-.PHONY: help install uninstall
+.PHONY: help install uninstall sync-skill
 
 help:
 	@echo "Usage: make [target]"
 	@echo ""
-	@echo "  install     Install mytoolkit in editable mode (current Python)"
+	@echo "  install     Install mytoolkit in editable mode (current Python) and sync skill"
+	@echo "  sync-skill  Copy the bundled Claude skill to ~/.claude/skills/mytoolkit/"
 	@echo "  uninstall   Uninstall mytoolkit and remove completions"
 
 install:
@@ -27,6 +28,17 @@ install:
 			echo "bash completion: $(COMP_DIR)/mytoolkit.bash" || \
 			echo "Warning: bash completion failed"; \
 	fi
+	@$(MAKE) -s sync-skill
+
+sync-skill:
+	@echo "Syncing Claude skill to ~/.claude/skills/mytoolkit/ ..."
+	@mkdir -p "$(HOME)/.claude/skills"
+	@if command -v rsync >/dev/null 2>&1; then \
+		rsync -av --delete "$(ROOT_DIR)/.claude/skills/mytoolkit/" "$(HOME)/.claude/skills/mytoolkit/"; \
+	else \
+		rm -rf "$(HOME)/.claude/skills/mytoolkit"; \
+		cp -R "$(ROOT_DIR)/.claude/skills/mytoolkit" "$(HOME)/.claude/skills/mytoolkit"; \
+	fi
 
 uninstall:
 	$(PYTHON) -m pip uninstall mytoolkit -y