chore(opencode): update to v1.1.51 and refactor build configuration

- Update opencode from v1.1.48 to v1.1.51
- Refactor build dependencies: remove fzf, add sysctl conditionally for Darwin
- Fix bun to use nixpkgs-unstable input instead of direct dependency
- Add platform-specific outputHash for Darwin and Linux
- Move wrapProgram from postFixup to installPhase
- Remove unnecessary build patch and postPatch/postBuild workarounds
- Fix config path to use absolute home directory
- Add git and home-manager to default shell inputs
- Minor README documentation reordering

README.md

@@ -87,10 +87,8 @@ fi
 4. Edit file
 
 ```bash
-# Ensure Config
-mkdir -p ~/.config/sops/age
-
 # Convert SSH to Age
+mkdir -p ~/.config/sops/age
 ssh-to-age -private-key -i $HOME/.ssh/id_ed25519 -o ~/.config/sops/age/keys.txt
 
 # Get Public Key