feat(github): add auto-conventional-commit hook with opencode integration

- Add prepare-commit-msg git hook that generates conventional commit messages
- Modularize fish configuration with separate conf.d files
- Convert configuration files from .text to .source format for structured data
- Add sops-nix SOPS configuration with explicit secret definitions
- Upgrade age identity to single key file management approach
- Add system activation script for age key management
- Generate .sops.yaml for SOPS creation rules
- Restructure README.md with improved table and cleaner formatting
- Refactor config files to use pkgs.formats.json/toml generators
- Implement YAML format for ashell and walker service configurations
- Update SSH config source to use sops secrets
- Convert zed and other config files to use structured .source format

secrets/age.key

@@ -0,0 +1,3 @@
+# created: 2026-07-12T10:20:38+02:00
+# public key: age1n2kvnwdzrd5vw70wwmm90a4lg6wj3665egzpnz72r98epr0rhc0q3yp356
+AGE-SECRET-KEY-1A49GYAG5AJWGW0XM7HWC8QFE6UUF0S3Z99T252SKX2JHW6NM0HDQESWAQC