fix(vscode): pin theme extensions for 10 marketplace palettes

Before this fix, only the 6 palettes whose theme extensions ship in
pkgs.vscode-extensions had working VSCode theming. Every other palette
had `workbench.colorTheme` set to a name VSCode couldn't find, so it
silently fell back to its built-in default. Including the DEFAULT
summer-night palette (sainnhe.everforest) — the default install had
broken VSCode theming.

Probed the 13 unique extensions against the VSCode marketplace
extensionquery API:

  - 10 exist and are pinnable: sainnhe.everforest,
    shadesOfBuntu.flexoki-light, qufiwefefwoyn.kanagawa,
    oldjobobo.{lumon,miasma,retro-82}-theme, TahaYVR.matteblack,
    jovejonovski.ocean-green, monokai.theme-monokai-pro-vscode,
    Bjarne.white-theme.
  - 3 don't exist on the marketplace and are unpublished custom
    Nomarchy themes: Bjarne.{ethereal,hackerman,vantablack}-nomarchy.
    Logged as a new Later row.

For the 10, fetched version + sha256 via:

  URL='https://${publisher}.gallery.vsassets.io/_apis/public/gallery/publisher/${publisher}/extension/${name}/${version}/assetbyname/Microsoft.VisualStudio.Services.VSIXPackage'
  nix store prefetch-file --hash-type sha256 "$URL"

Added a marketplaceExtensions list to features/apps/vscode.nix that
wraps each in pkgs.vscode-utils.extensionFromVscodeMarketplace and
concatenates with the existing nixpkgs-packaged list — so 10 more
palettes (including the default) now get correct VSCode theming on
first launch. Smoke-built sainnhe.everforest end-to-end. Module
comment documents the version-bump procedure.

docs/OPTIONS.md updated: the nomarchy.vscode.devExtensions entry
drops the "still break" caveat for everything except the three
unpublished Bjarne palettes.

`nix flake check --no-build` clean.

features/apps/vscode.nix

@@ -7,24 +7,76 @@ let
   else
     { name = "Default Dark Modern"; };
 
-  # Theme extensions matching palette vscode.json `extension` fields. Always
-  # installed because workbench.colorTheme is set unconditionally from the
-  # active palette — without the matching extension VSCode silently falls
-  # back to its default theme. Only the extensions available in
-  # pkgs.vscode-extensions are listed. Palettes whose theme extension is on
-  # the VSCode marketplace but not packaged in nixpkgs (sainnhe.everforest —
-  # affects the DEFAULT summer-night palette — plus qufiwefefwoyn.kanagawa,
-  # monokai.theme-monokai-pro-vscode, oldjobobo.*, Bjarne.*,
-  # shadesOfBuntu.flexoki-light, jovejonovski.ocean-green, TahaYVR.matteblack)
-  # still break and need pkgs.vscode-utils.extensionFromVscodeMarketplace —
-  # tracked in ROADMAP Later.
-  themeExtensions = with pkgs.vscode-extensions; [
+  # Theme extensions matching palette vscode.json `extension` fields.
+  # Always installed because workbench.colorTheme is set unconditionally
+  # from the active palette — without the matching extension VSCode
+  # silently falls back to its default theme.
+  #
+  # The list is split because nixpkgs doesn't package every theme our
+  # palettes use. Six are in pkgs.vscode-extensions; the rest are pulled
+  # from the VSCode marketplace via extensionFromVscodeMarketplace with
+  # publisher / name / version / sha256 pinned. To refresh a version,
+  # bump the `version` and `nix-prefetch-url` the new .vsix:
+  #
+  #   URL='https://${publisher}.gallery.vsassets.io/_apis/public/gallery/publisher/${publisher}/extension/${name}/${version}/assetbyname/Microsoft.VisualStudio.Services.VSIXPackage'
+  #   nix store prefetch-file --hash-type sha256 "$URL"
+  #
+  # Three palette extensions remain unfixed because the corresponding
+  # marketplace entries don't exist — Bjarne.ethereal-nomarchy,
+  # Bjarne.hackerman-nomarchy, Bjarne.vantablack-nomarchy. The matching
+  # palettes (ethereal, hackerman, vantablack) still fall back to
+  # VSCode's default theme; see the ROADMAP Later row for next steps.
+
+  marketplaceExtensions = with pkgs.vscode-utils; [
+    (extensionFromVscodeMarketplace {           # everforest, summer-day, summer-night
+      publisher = "sainnhe"; name = "everforest"; version = "0.3.0";
+      sha256 = "sha256-nZirzVvM160ZTpBLTimL2X35sIGy5j2LQOok7a2Yc7U=";
+    })
+    (extensionFromVscodeMarketplace {           # flexoki-light
+      publisher = "shadesOfBuntu"; name = "flexoki-light"; version = "1.0.0";
+      sha256 = "sha256-//y9uvIUGGDEhd8inDHvNy2e1IKNx6hSfO9sxNOTcUE=";
+    })
+    (extensionFromVscodeMarketplace {           # kanagawa
+      publisher = "qufiwefefwoyn"; name = "kanagawa"; version = "1.5.1";
+      sha256 = "sha256-AGGioXcK/fjPaFaWk2jqLxovUNR59gwpotcSpGNbj1c=";
+    })
+    (extensionFromVscodeMarketplace {           # lumon
+      publisher = "oldjobobo"; name = "lumon-theme"; version = "0.0.7";
+      sha256 = "sha256-YlO1r1JjaumiicvMk5fBr+PZCYFaII03PaLiyqE35Go=";
+    })
+    (extensionFromVscodeMarketplace {           # matte-black
+      publisher = "TahaYVR"; name = "matteblack"; version = "1.0.3";
+      sha256 = "sha256-wn/llGidzyPd91XT3xVqAvaU4NcTTggTSz8WmUcV8HM=";
+    })
+    (extensionFromVscodeMarketplace {           # miasma
+      publisher = "oldjobobo"; name = "miasma-theme"; version = "0.1.1";
+      sha256 = "sha256-STFTGFhQqxocr+YNFQp36IQWJRKTDBgBg4MOCOq1IPQ=";
+    })
+    (extensionFromVscodeMarketplace {           # osaka-jade
+      publisher = "jovejonovski"; name = "ocean-green"; version = "1.1.2";
+      sha256 = "sha256-sUNjnzqXya23Uieg8RLcEfnxiX0ImZ6CIjFtSJ66vM4=";
+    })
+    (extensionFromVscodeMarketplace {           # retro-82
+      publisher = "oldjobobo"; name = "retro-82-theme"; version = "0.1.4";
+      sha256 = "sha256-GqFeFFG5scO7CEXlKjj6uoilCoUfpRaQa5jBSnNJyJA=";
+    })
+    (extensionFromVscodeMarketplace {           # ristretto
+      publisher = "monokai"; name = "theme-monokai-pro-vscode"; version = "2.0.13";
+      sha256 = "sha256-5bKwVzDfZoSipR04tPDx9jbKhYsSsa3z6Ei9E2jhudo=";
+    })
+    (extensionFromVscodeMarketplace {           # white
+      publisher = "Bjarne"; name = "white-theme"; version = "0.0.1";
+      sha256 = "sha256-3ZyWNVlQO3Tof49FFF3OImuo7hgtJXLNuwQ+iHjzzGk=";
+    })
+  ];
+
+  themeExtensions = (with pkgs.vscode-extensions; [
     catppuccin.catppuccin-vsc                  # catppuccin, catppuccin-latte
     enkia.tokyo-night                          # tokyo-night
     arcticicestudio.nord-visual-studio-code    # nord
     mvllow.rose-pine                           # rose-pine
     jdinhlife.gruvbox                          # gruvbox
-  ];
+  ]) ++ marketplaceExtensions;
 
   # Development extensions — opt-in via nomarchy.vscode.devExtensions.
   devExtensions = with pkgs.vscode-extensions; [