docs: align documentation with framework reality (.agents, .mdc, missing skills and rules)

docs: update root files to reflect .agents migration and correct rule extensions

fix(mesh): replace .antigravity with .agents and .md with .mdc in rules and skills

fix(bin): migrate init.sh from .antigravity to .agents and use .mdc rule extension

chore(bin): align comment in _lib.sh with private repo wording

feat(mesh): add ai-files-language rule for AI configuration files

feat(claude): add PreToolUse hooks and project_health command

feat(mesh): introduce mAIcelium identity framework documentation

feat(mesh): add _clients tier, MCP config generation, and project data symlinks

refactor: update file extensions and enhance symlink management for mAIcelium rules

docs: update CLAUDE.md and settings.json to enhance session initialization

fix: update sync_symlinks.sh to use -L flag for finding broken symlinks

refactor: add YAML frontmatter to commands and skills, and rename .antigravity directory to .agents

feat: add Cursor workspace migration tool, project health script, and standardized skill documentation templates

chore: add execute permission to separate_git.sh