refactor: reorganize, add package (opencode, osgrep, beads), add ai agent shell

devshells/web-bun.nix

@@ -1,21 +0,0 @@
-{ pkgs, ... }:
-
-pkgs.mkShell {
-  name = "web-bun";
-  packages = with pkgs; [
-    bun
-    nodejs_20
-    yarn
-    esbuild
-    vscode-langservers-extracted
-  ];
-  shellHook = ''
-    mkdir -p "$PWD/.cache/bun"
-    export BUN_INSTALL_CACHE="$PWD/.cache/bun"
-    ccusage() { bunx ccusage "$@"; }
-    export -f ccusage
-    echo "Bun/Node web shell ready"
-    echo "Bun: ${pkgs.bun.version}"
-    echo "Node: ${pkgs.nodejs_20.version}"
-  '';
-}