feat(shell.nix): configure htop settings and meters

Flesh out programs.htop: tree view, sensible highlights, hidden kernel
threads, left CPU/Memory/Swap bar meters and right Tasks/LoadAverage/Uptime
text meters. color_scheme = 0 inherits the terminal's Catppuccin Mocha
palette, as htop has no custom-theme support of its own.

Drop the explicit pkgs.htop: programs.htop.enable already installs it.

lyrathorpe/home/shell.nix

@@ -26,7 +26,6 @@ in
     pkgs.tea
     pkgs.hyperfine # command-line benchmarking
     pkgs.sd # saner find-and-replace than sed
-    pkgs.htop # ensure there's a system monitor
   ];
 
   # Resource monitor, themed Catppuccin Mocha to match the rest of the desktop.
@@ -346,8 +345,58 @@ in
   # enables this in the work module; both being true merges cleanly.
   services.ssh-agent.enable = lib.mkIf pkgs.stdenv.hostPlatform.isLinux true;
 
+  # Classic process viewer (complements btop). htop has no custom-theme support
+  # -- only a handful of built-in color schemes -- so it can't be hex-themed like
+  # btop/bat/fzf. color_scheme = 0 (Default) draws from the terminal's ANSI
+  # palette, which is Catppuccin Mocha (foot/iTerm2), so it matches by deferring
+  # to the terminal rather than vendoring a theme.
   programs.htop = {
     enable = true;
+    settings = {
+      color_scheme = 0; # Default -> uses the terminal's Catppuccin palette
+      delay = 15; # refresh every 1.5s
+      cpu_count_from_one = 1;
+      show_cpu_frequency = 1;
+      show_cpu_usage = 1; # per-core usage shown in the CPU bars
+      highlight_base_name = 1; # highlight the program name within the path
+      highlight_megabytes = 1;
+      highlight_threads = 1;
+      hide_kernel_threads = 1;
+      show_program_path = 0; # show just the command, not the full path
+      tree_view = 1; # start in process-tree mode
+      tree_view_always_by_pid = 0;
+      account_guest_in_cpu_meter = 0;
+      fields = with config.lib.htop.fields; [
+        PID
+        USER
+        PRIORITY
+        NICE
+        M_SIZE
+        M_RESIDENT
+        M_SHARE
+        STATE
+        PERCENT_CPU
+        PERCENT_MEM
+        TIME
+        COMM
+      ];
+    }
+    // (
+      with config.lib.htop;
+      leftMeters [
+        (bar "AllCPUs2")
+        (bar "Memory")
+        (bar "Swap")
+      ]
+    )
+    // (
+      with config.lib.htop;
+      rightMeters [
+        (text "Tasks")
+        (text "LoadAverage")
+        (text "Uptime")
+      ]
+    );
   };
 
   # Drop the zsh completion dump on every activation. A stale .zcompdump caches