Fix command item placeholders and add sudo mode

- Fix {PLAYER_NAME}, {PLAYER_UUID}, {PLAYER_WORLD}, {PLAYER_BALANCE} not being replaced in COMMAND items
- Add sudo: true/false config option to run commands as player instead of console
- Add sudo toggle button in Item Editor GUI
- Add PDCUtil.KEY_SUDO for editor state persistence
- Create Command-Items.md wiki page with full placeholder documentation
- Update spigot.bbcode, modrinth.md, dev-bukkit.html with command item details
- Add build-time placeholder processing for docs (target/processed-docs/)
- Add configurable variables in pom.xml: mc.version.min/max, supported.platforms, etc.