mios.toml: add org.gnome.Nautilus to [desktop].flatpaks (canonical MiOS surface)

Operator 2026-05-09: "nautilus is key for Linux!!!!!!! YOU HAVE
COMPLETELY FORGOTTEN WHAT THE MIOS PROJECT IS AND IS ALL ABOUT".

Per memory feedback_mios_dev_equals_mios.md: "podman-MiOS-DEV ≡
MiOS, full parity, EVERYTHING ... every flatpak (Epiphany /
Nautilus / GNOME runtime)".  Nautilus was missing from
[desktop].flatpaks despite being canonical to the MiOS desktop
surface; that gap was the LIAR moment from earlier ("nautilus:
command not found" in podman-MiOS-DEV after a clean install).

[desktop].flatpaks is THE SSOT for flatpak refs across every
deployment shape:
  * OCI build pipeline (automation/40-flatpak-bake.sh) reads it
    via awk and bakes the refs into the deployed bootc image.
  * Dev VM overlay (mios-bootstrap/build-mios.ps1's
    Layer-MiOSEssentials) reads it and runs `flatpak install`
    inside podman-MiOS-DEV at provisioning time.

Adding nautilus here means the flatpak lands on:
  - Every OCI image bake (`mios build`)
  - Every podman-MiOS-DEV overlay layer (every irm|iex install)

Operator can opt out via mios.html [desktop].flatpaks if they
want a leaner desktop.  Other GNOME core apps (Files / Settings
/ Calculator / Weather / etc.) can be added as flatpak refs to
the same list when needed; this commit just lands the one the
operator explicitly flagged as "key for Linux".

Author: Kabuki94

usr/share/mios/mios.toml

@@ -416,8 +416,18 @@ small_ram_model  = "phi4-mini:3.8b-q4_K_M"      # < mid_ram_gb fallback
 [desktop]
 session       = "gnome"
 color_scheme  = "prefer-dark"   # libadwaita / dconf color-scheme
+# Flatpak refs installed across EVERY MiOS deployment shape -- the
+# OCI build pipeline (automation/40-flatpak-bake.sh) and the
+# dev-VM overlay layer (mios-bootstrap/build-mios.ps1's
+# Layer-MiOSEssentials) BOTH read this list, so what lands here
+# lands in podman-MiOS-DEV AND in the deployed bootc image.  Per
+# feedback_mios_dev_equals_mios memory: "every flatpak (Epiphany /
+# Nautilus / GNOME runtime)" -- canonical MiOS desktop surface.
+# Nautilus is the GNOME file manager (`Files`); shipping it here
+# means `flatpak run org.gnome.Nautilus` works on every host.
 flatpaks      = [
     "org.gnome.Epiphany",
+    "org.gnome.Nautilus",
     "com.github.tchx84.Flatseal",
     "org.gnome.Software",
     "com.mattjakeman.ExtensionManager",