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

lib/default.nix

@@ -0,0 +1,11 @@
+# lib/default.nix — Entry point for m3ta-home library functions.
+#
+# Provides:
+#   mkHome     — compose a complete HM config from user + identity + context + sets
+#   mkDevShell — create project-level dev shells from language sets
+{inputs}: {
+  mkHome = import ./mkHome.nix {inherit inputs;};
+
+  # TODO: mkDevShell for project-level flake devShells
+  # mkDevShell = import ./mkDevShell.nix { inherit inputs; };
+}

lib/mkHome.nix

@@ -0,0 +1,103 @@
+# lib/mkHome.nix — Compose a complete home-manager configuration.
+#
+# This is the central function that replaces the old mkHomeConfig from nixos-config.
+# It assembles imports based on three dimensions:
+#
+#   WHO you are  →  user + identity (preferences + git/ssh/jj config)
+#   WHAT you do  →  context (desktop|server) + sets (coding, gaming, media)
+#   WHERE you are →  host (handled by nixos-config, only overrides here)
+#
+# Usage:
+#   imports = [ (m3ta-lib.mkHome {
+#     user = "m3tam3re";
+#     identity = "private";     # or "work"
+#     context = "desktop";      # or "server"
+#     sets = [ "coding" "gaming" "media" ];
+#   }) ];
+#
+# Then override host-specific settings in the consuming module:
+#   m3ta.home.sets.coding.languages.python.extra = true;
+#   wayland.windowManager.hyprland.settings.monitor = [ ... ];
+#
+{inputs}:
+{lib ? inputs.nixpkgs.lib}:
+let
+  # --- Module path helpers ---
+  profilePath = ../profiles;
+  userPath = ../users;
+
+  # Always loaded — CLI tools, shell, secrets, overlays
+  baseModule = "${profilePath}/base";
+
+  # Context modules — mutually exclusive (desktop or server)
+  contextModuleMap = {
+    desktop = "${profilePath}/contexts/desktop";
+    server = "${profilePath}/contexts/server";
+  };
+
+  # Feature sets — freely combinable, some have context guards
+  setModuleMap = {
+    coding = "${profilePath}/sets/coding";
+    gaming = "${profilePath}/sets/gaming";
+    media = "${profilePath}/sets/media";
+  };
+
+  # Sets that require desktop context
+  desktopOnlySets = ["gaming" "media"];
+in {
+  mkHome = {
+    user ? "m3tam3re",
+    identity ? "private",
+    context ? null,
+    sets ? [],
+  }: let
+    # User preferences — always loaded (shell style, editor config, etc.)
+    preferencesPath = "${userPath}/${user}/preferences";
+
+    # Identity — git name/email, SSH match blocks, jj config
+    identityPath = "${userPath}/${user}/identities/${identity}.nix";
+
+    # Resolve context module
+    contextImport =
+      if context == null
+      then []
+      else if builtins.hasAttr context contextModuleMap
+      then [contextModuleMap.${context}]
+      else throw "m3ta-home: unknown context '${context}'. Valid: desktop, server";
+
+    # Resolve set modules
+    setImports =
+      map
+      (s:
+        if builtins.hasAttr s setModuleMap
+        then setModuleMap.${s}
+        else throw "m3ta-home: unknown set '${s}'. Valid: ${lib.concatStringsSep ", " (builtins.attrNames setModuleMap)}")
+      sets;
+
+    # Validation: desktop-only sets
+    usedDesktopOnlySets =
+      builtins.filter (s: builtins.elem s desktopOnlySets) sets;
+  in {
+    imports =
+      [
+        baseModule
+        preferencesPath
+        identityPath
+      ]
+      ++ contextImport
+      ++ setImports;
+
+    assertions =
+      [
+        {
+          assertion = builtins.elem context ["desktop" "server" null];
+          message = "m3ta-home: context must be 'desktop', 'server', or null (got: '${toString context}')";
+        }
+      ]
+      ++ map (s: {
+        assertion = context == "desktop";
+        message = "m3ta-home: set '${s}' requires context = 'desktop'";
+      })
+      usedDesktopOnlySets;
+  };
+}