Merge pull request 'fix(siri): add venv to the siril installation' (#77) from fix/siril into main

Reviewed-on: #77

modules/nixos/astro.nix

@@ -15,7 +15,15 @@ let
     # on PATH. nixpkgs only *propagates* python3 from the siril derivation (it
     # isn't on the runtime PATH), so without the --prefix PATH below the GUI
     # fails with "Python not found in system PATH" and never creates
-    # ~/.local/share/siril/venv. We add the same interpreter siril references.
+    # ~/.local/share/siril/venv.
+    #
+    # We deliberately do NOT put ${pkgs.python3}/bin on PATH directly: `venv`
+    # symlinks bin/python3 to whatever sys.executable was, so the venv would
+    # hard-link a /nix/store hash that gets garbage-collected after the next
+    # python bump, leaving a dangling symlink ("Error finding venv python
+    # path, unable to spawn python"). Instead we go through the stable
+    # /etc/siril/bin/python3 symlink (see environment.etc below), which NixOS
+    # re-points at the current python on every rebuild.
     #
     # The VeraLux PyQt6 wheel ships only the built-in Windows/Fusion styles, so
     # the global QT_STYLE_OVERRIDE=adwaita-dark (inherited from the session) is
@@ -26,7 +34,7 @@ let
     # ignored again (harmless warning + Fusion fallback, no loss of function).
     postBuild = ''
       wrapProgram $out/bin/siril \
-        --prefix PATH : ${lib.makeBinPath [ pkgs.python3 ]} \
+        --prefix PATH : /etc/siril/bin \
         --prefix QT_PLUGIN_PATH : ${pkgs.adwaita-qt6}/lib/qt-6/plugins \
         --prefix LD_LIBRARY_PATH : ${lib.makeLibraryPath (with pkgs; [
           stdenv.cc.cc.lib   # libstdc++ / libgcc_s / libgomp  (numpy etc.)
@@ -62,6 +70,10 @@ in
     sirilWithPlugins
   ];
 
+  # Stable, GC-safe interpreter path for Siril's venv (see sirilWithPlugins).
+  # Same python as siril itself propagates, so sirilpy's ABI matches.
+  environment.etc."siril/bin/python3".source = "${pkgs.python3}/bin/python3";
+
   # StarNet++ has no nixpkgs package. Download the StarNet v2 ORT CLI build
   # (starnet2_linux_*_ORT_x64_cli) from https://www.starnetastro.com/download/
   # and unzip it to ~/.local/share/siril/starnet/. Then in Siril set