Stage 1: extract the skin-agnostic UI layer into app/core/

First step of splitting the UI into two skin trees. All 12 services plus
platform.ts, format.ts, file-icons.ts, icons.ts and app.config.ts move to
ui/src/app/core/ — the layer both skins will share.

This is a pure move: git records all 17 as renames, and no file content
changed beyond import paths. The premise holds because `git diff
main...feat/7css-skin` touches none of these files — the service layer was
already skin-agnostic, so there is nothing to untangle, only to relocate.

Components now reach it through a new `@core/*` tsconfig alias rather than a
relative path. That is deliberate and load-bearing for the next stage: skin
components are about to move under app/skins/<skin>/ at varying depths, and
an alias keeps every one of these 67 imports correct wherever its file ends
up. `@shared/*` (the bun-side src/shared) already set the precedent.

Intra-core imports needed no edits at all — every ./sibling reference among
the moved files points at another moved file.

Verified: tsc clean, `bun run build:ui` clean (AOT resolves every import and
template symbol), and the running window's opaque interior is pixel-identical
to a pre-refactor capture.

Note on that comparison: the Aero frame and title bar do NOT compare equal
between launches, and that is not a regression — .window.glass::before runs
at opacity .6, so the chrome composites over whatever desktop is behind the
window and shifts by a uniform ~8% brightness. The check therefore diffs the
opaque interior (inset 30px sides, 80px top), where anything this refactor
could break would show.

Co-Authored-By: Claude <noreply@anthropic.com>

ui/src/app/core/file-icons.ts

@@ -0,0 +1,105 @@
+// File-list glyphs + per-category colors ("Multi" icon mode). Category colors
+// are fixed tokens (never follow the accent) so a folder is always folder-blue.
+// Only the icon glyph is colored; row text stays neutral. Docs and unknown
+// files stay muted on purpose — sparing color is what keeps it scannable.
+import type { FileEntry } from '@shared/types';
+
+type Category = 'image' | 'audio' | 'video' | 'archive' | 'code' | 'doc';
+
+// Class strings are literals so the Tailwind scanner picks them up.
+const MUTED = 'shrink-0 text-muted-foreground';
+const PRIMARY = 'shrink-0 text-primary';
+const FOLDER = 'shrink-0 text-icon-folder';
+const LINK = 'shrink-0 text-icon-link';
+
+const CATEGORIES: Record<Category, { glyph: string; class: string; extensions: string[] }> = {
+  image: {
+    glyph: 'mynaImage',
+    class: 'shrink-0 text-icon-image',
+    extensions: 'png jpg jpeg gif webp avif svg ico icns bmp tiff tif heic heif raw'.split(' '),
+  },
+  audio: {
+    glyph: 'mynaMusic',
+    class: 'shrink-0 text-icon-media',
+    extensions: 'mp3 wav flac aac ogg oga m4a opus wma aiff aif mid midi'.split(' '),
+  },
+  video: {
+    glyph: 'mynaVideo',
+    class: 'shrink-0 text-icon-media',
+    extensions: 'mp4 mkv mov avi webm m4v mpg mpeg wmv flv 3gp'.split(' '),
+  },
+  archive: {
+    glyph: 'mynaArchive',
+    class: 'shrink-0 text-icon-archive',
+    extensions: 'zip tar gz tgz bz2 xz zst 7z rar dmg iso jar deb rpm pkg apk'.split(' '),
+  },
+  code: {
+    glyph: 'mynaCode',
+    class: 'shrink-0 text-icon-code',
+    // ".ts" is TypeScript here, not an MPEG transport stream (deliberate)
+    extensions: (
+      'js mjs cjs ts tsx jsx json jsonc yaml yml toml xml html htm css scss sass less ' +
+      'py rb go rs java kt kts swift c h cpp hpp cc m mm cs php sh bash zsh fish ps1 bat ' +
+      'sql lua pl r vue svelte astro ini conf cfg env plist gradle cmake nix proto graphql ' +
+      'dart ex exs zig lock makefile dockerfile zshrc bashrc bash_profile profile ' +
+      'gitignore gitconfig gitattributes editorconfig npmrc nvmrc'
+    ).split(' '),
+  },
+  doc: {
+    glyph: 'mynaFileText',
+    class: MUTED, // docs keep the neutral color; only the glyph changes
+    extensions: 'md markdown txt rtf pdf doc docx xls xlsx ppt pptx csv tsv log odt ods odp epub'.split(' '),
+  },
+};
+
+const EXT_CATEGORY = new Map<string, Category>();
+for (const category of Object.keys(CATEGORIES) as Category[]) {
+  for (const ext of CATEGORIES[category].extensions) EXT_CATEGORY.set(ext, category);
+}
+
+/** "a.tar.gz" -> "gz"; ".zshrc" -> "zshrc"; "Makefile" (no dot) -> "makefile". */
+function categoryOf(name: string): Category | null {
+  const dot = name.lastIndexOf('.');
+  const key = (dot >= 0 ? name.slice(dot + 1) : name).toLowerCase();
+  return EXT_CATEGORY.get(key) ?? null;
+}
+
+const KIND_KEYS: Record<Category, string> = {
+  image: 'image',
+  audio: 'audio',
+  video: 'video',
+  archive: 'archive',
+  code: 'code',
+  doc: 'document',
+};
+
+/**
+ * i18n key suffix for the optional Kind column (category-based, like the
+ * icons); '' for the synthetic '..' row. The caller resolves `kinds.<suffix>`.
+ */
+export function fileKindKey(entry: FileEntry): string {
+  if (entry.name === '..') return '';
+  if (entry.type === 'dir') return 'folder';
+  if (entry.type === 'symlink') return 'symlink';
+  const category = categoryOf(entry.name);
+  return category ? KIND_KEYS[category] : 'file';
+}
+
+export function fileGlyph(entry: FileEntry, multi: boolean): string {
+  if (entry.name === '..') return 'mynaArrowUp';
+  if (entry.type === 'dir') return 'mynaFolder';
+  if (!multi) return 'mynaFile';
+  if (entry.type === 'symlink') return 'mynaLink';
+  const category = categoryOf(entry.name);
+  return category ? CATEGORIES[category].glyph : 'mynaFile';
+}
+
+export function fileIconClass(entry: FileEntry, multi: boolean): string {
+  // plain mode: exactly the pre-color look ('..' has type 'dir' -> primary)
+  if (!multi) return entry.type === 'dir' ? PRIMARY : MUTED;
+  if (entry.name === '..') return MUTED;
+  if (entry.type === 'dir') return FOLDER;
+  if (entry.type === 'symlink') return LINK;
+  const category = categoryOf(entry.name);
+  return category ? CATEGORIES[category].class : MUTED;
+}