feat: add Nix flake packaging support

[yebei199]

Summary

• Add Nix flake support (flake.nix, flake.lock) for reproducible builds and development environments.
• Update project dependencies and upgrade oh-my-opencode platform-specific binaries to 3.0.0-beta.11.
• Clean up unused dependencies and update .gitignore for Nix-related build artifacts.

Changes

• Infrastructure: Added flake.nix and flake.lock to support Nix-based workflows.
  • Defined oh-my-opencode package for Linux and Darwin.
  • Added a node_modules derivation with fixed-output hash for Bun installations.
  • Configured a default devShell with bun and nodejs_24.
• Dependencies:
  • Upgraded optional platform-specific dependencies from 3.0.0-beta.8 to 3.0.0-beta.11.
  • Removed several unused packages: @openauthjs/openauth, hono, open, xdg-basedir, and their transitive dependencies.
• Git: Added result/ (Nix build symlink) to .gitignore.

Testing

Verified the build process and environment stability.

# Verify Nix flake build
nix build .#oh-my-opencode

# Standard checks
bun run typecheck
bun test

Related Issues

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Summary by cubic

Adds Nix flake support to package oh-my-opencode and provide a reproducible dev environment. This improves onboarding and keeps builds consistent on Linux and macOS.

• New Features
  • Added flake.nix/flake.lock to build oh-my-opencode for Linux and macOS with fixed-output Bun node_modules, autoPatchelf, and a default devShell (bun, nodejs_24).
  • Added result/ to .gitignore.
  • Enabled ultrawork mode in ralphLoop.

^{Written for commit 25103f1. Summary will update on new commits.}

#1268

[yebei199]

close #1268

[yebei199]

.