feat: initial m3ta-home structure

- flake.nix with nixpkgs, home-manager, nix-colors, m3ta-nixpkgs, agenix, NUR inputs
- lib/mkHome.nix: compose HM config from user + identity + context + sets
- profiles/base: shell, cli-tools, secrets (always loaded)
- profiles/contexts/desktop: WM, apps, theme, ghostty
- profiles/contexts/server: minimal headless
- profiles/sets/coding: core (git, direnv, jq, rg), editor, lsp, languages, agents
- profiles/sets/gaming: steam, gamescope, gpu
- profiles/sets/media: obs, ffmpeg, kdenlive, handbrake, yt-dlp
- users/m3tam3re/identities: private.nix, work.nix (git, jj, ssh per identity)
- users/m3tam3re/preferences: cliphist, difftastic, base packages

profiles/sets/coding/default.nix

@@ -0,0 +1,22 @@
+# profiles/sets/coding/default.nix — Coding environment aggregator.
+#
+# Imports all coding sub-modules. Individual features are controlled
+# via enable options (e.g. coding.editors.neovim.enable = true).
+#
+# Structure:
+#   core/       — Always-on when coding set is active (git, direnv, core packages)
+#   editor/     — Neovim (both contexts), Zed (desktop only)
+#   lsp/        — Language server protocol tools
+#   languages/  — Python, JS, Rust, Go, TypeScript (each with enable option)
+#   agents/     — AI coding agents (opencode, etc.)
+#   packages    — Optional extra packages (bruno, insomnia)
+{...}: {
+  imports = [
+    ./core
+    ./editor
+    ./lsp
+    ./agents/agents.nix
+    ./languages
+    ./packages.nix
+  ];
+}