fix: update zsh options and add greeter user for greetd

Co-authored-by: aider (openrouter/openai/gpt-5.2) <aider@aider.chat>

docs/nixos_build_spec.md

@@ -36,8 +36,10 @@ Bootloader:
 
 ## Desktop
 - Primary compositor: Niri
-- Display/login manager: TBD (recommend greetd)
-- GPU: Intel HD 630 + NVIDIA Quadro P620 (confirm which drives monitors)
+- Display/login manager: greetd + tuigreet
+- Session start command: `niri --session` (do not use `niri-session`)
+- GPU: Intel HD 630 + NVIDIA Quadro P620
+- Display appears to be driven by NVIDIA Quadro P620 (observed `/dev/fb0` on Ubuntu scan). Treat NVIDIA as primary unless proven otherwise.
 
 ## Secrets policy
 - No API keys or WiFi PSKs committed to git

docs/software_inventory.md

@@ -17,7 +17,7 @@ Legend:
 - **niri** (primary compositor)
 - **greetd + tuigreet** (display/login manager)
 - **xwayland** (X11 compatibility where needed)
-- **xdg-desktop-portal** + **xdg-desktop-portal-gtk** (portals for file pickers / screen share baseline)
+- **xdg-desktop-portal** + **xdg-desktop-portal-gtk** + **xdg-desktop-portal-gnome** (portals baseline; improves screencast/screen share odds)
 - Clipboard:
   - **wl-clipboard**
 - Screenshots (Wayland):