feat: comment out nixpkgs-unstable, we use unstable by default

[ryan4yin]

Note

Introduce nixpkgs-master for select latest packages and remove nixpkgs-unstable, updating modules to source from pkgs or pkgs-master and making minor package/config tweaks.

• Inputs/Outputs:
  • Add inputs.nixpkgs-master and expose pkgs-master in outputs/default.nix.
  • Remove inputs.nixpkgs-unstable and its pkgs-unstable usages (commented out in outputs).
• Nixpaks:
  • Switch nixpaks.qq to build via pkgs-master.
• Editors/Dev Tooling:
  • Neovim: use pkgs.neovim-unwrapped (was pkgs-unstable).
  • Editor packages: source hugo and Rust toolchain (rustc, cargo, rustfmt, clippy, rust-analyzer) from pkgs-master.
  • Linux GUI editors: install zed-editor and custom cursor from pkgs-master.
• GUI/Misc:
  • OBS plugins list flattened; include obs-vaapi and obs-3d-effect directly; keep obs-studio.enable gated to x86_64.
  • Use nixpaks.qq, nixpaks.telegram-desktop, and bwraps.wechat without pkgs. prefix.
  • Media package list simplified (same contents).
• Shells & Peripherals:
  • Darwin shells: use pkgs.nushell.
  • General cleanup of commented -unstable package lines.
• Hosts:
  • Apple Silicon host: use pkgs for system packages and pkgs.tiny-dfr for touch bar.
• Lockfile:
  • Lock updates reflecting added nixpkgs-master and removal of nixpkgs-unstable reference.

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