Session overhaul: dev tooling, cleanup, theming, fixes

Tooling:
- nh + nvd/nom/statix/deadnix/comma (new programs/nix.nix); GC via nh clean
- zoxide (cd), atuin, just, lazydocker, dust, duf, difftastic (git dft)

Structure:
- rename desktop -> konishi; homeConfigurations -> "user@host" for nh autodetect

Removals (heavy/unused):
- android-studio, unity/.NET/omnisharp/vscode, kicad, zoom, calibre,
  google-fonts, nerd-dictation

Screen recording:
- kooha + vokoscreen-ng + `webcam` corner-cam command/window-rule

Fixes:
- WEBKIT_DISABLE_DMABUF_RENDERER moved to common (electron/tauri on intel)
- kitty pinned to Catppuccin-Mocha; darkman no longer toggles kitty/claude
- claude theme dark + statusline locale fix
- ssh: migrate to settings API + multiplexing/keepalive/AddKeysToAgent;
  gpg-agent enableSshSupport
- silence hyprland configType / gtk4 / xdg userDirs deprecations

Flake hygiene:
- follows=nixpkgs for foundry/hardware/rose-pine/zen/spicetify (10->5 nixpkgs)
- zoxide _ZO_DOCTOR=0

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

home/common/programs/hyprland/default.nix

@@ -6,6 +6,19 @@
 }:
 let
   cfg = config.custom.hyprland;
+
+  # Floating webcam preview for the "corner-cam" recording trick: run `webcam`,
+  # then capture the whole screen with kooha/wf-recorder — the preview is in the
+  # recording. v4l2 only (won't work with the laptop's IPU6 cam). Optional device
+  # arg, e.g. `webcam /dev/video2`.
+  webcam = pkgs.writeShellScriptBin "webcam" ''
+    dev="''${1:-/dev/video0}"
+    exec ${pkgs.mpv}/bin/mpv \
+      --profile=low-latency --untimed \
+      --no-osc --no-input-default-bindings \
+      --title=webcam-overlay --border=no --ontop \
+      "av://v4l2:$dev"
+  '';
 in
 {
   options.custom.hyprland = {
@@ -39,6 +52,7 @@ in
       cliphist
       wf-recorder
       slurp
+      webcam
     ];
 
     home.sessionVariables = {
@@ -129,13 +143,18 @@ in
           "XCURSOR_SIZE, ${toString cfg.cursorSize}"
           "HYPRCURSOR_THEME, rose-pine-hyprcursor"
           "HYPRCURSOR_SIZE, ${toString cfg.cursorSize}"
+          # Route Qt6 apps (incl. the xdph screen-share picker) through qt6ct so
+          # the noctalia-generated color scheme actually applies. Without this
+          # var the qt6ct.conf is never read.
+          "QT_QPA_PLATFORMTHEME, qt6ct"
         ];
 
         "exec-once" = [
-          "dbus-update-activation-environment --systemd WAYLAND_DISPLAY XDG_CURRENT_DESKTOP"
+          # Import the Qt theme var too, so the dbus/systemd-activated
+          # xdg-desktop-portal-hyprland (and its share-picker) inherit it.
+          "dbus-update-activation-environment --systemd WAYLAND_DISPLAY XDG_CURRENT_DESKTOP QT_QPA_PLATFORMTHEME"
           "hyprctl setcursor Nordzy-cursors ${toString cfg.cursorSize}"
           "hyprsunset"
-          "nerd-dictation begin --simulate-input-tool WTYPE --suspend-on-start && touch ~/.cache/nerd-dictation-suspended"
           "noctalia"
         ];
 
@@ -167,6 +186,15 @@ in
           "size 1920 1080, match:class mpv"
           "move (cursor_x-(window_w*0.5)) (cursor_y-(window_h*0.5)), match:class mpv"
 
+          # webcam overlay (`webcam` command) — small, pinned, bottom-right.
+          # Title rules come after the mpv class rules so they win.
+          "float on, match:title webcam-overlay"
+          "size 360 240, match:title webcam-overlay"
+          "move 100%-380 100%-260, match:title webcam-overlay"
+          "pin on, match:title webcam-overlay"
+          "no_initial_focus on, match:title webcam-overlay"
+          "border_size 0, match:title webcam-overlay"
+
 
           # thunar
           "float on, match:class thunar"