refactor: restructure project into muxplex/ subdir with brand integration

- Move coordinator/, frontend/, Caddyfile, pyproject.toml, requirements.txt,
  docs/ into muxplex/ subdir in prep for packaging/sharing
- Add brand assets to frontend/: favicon.ico, pwa-192/512.png,
  apple-touch-icon.png, wordmark-on-dark.svg
- Update app: title → muxplex, header → wordmark SVG, brand color tokens
  in style.css, manifest.json updated with muxplex name and brand icons
- Add design system: assets/branding/tokens.css (101 CSS custom properties),
  tokens.json (127 tokens), DESIGN-SYSTEM.md (856-line spec)
- Add assets/branding/: SVG sources, rendered PNGs (icons, favicons, PWA, OG)
- Add scripts/render-brand-assets.py for reproducible PNG generation
- Add muxplex/README.md

coordinator/tests/test_frontend_css.py

@@ -0,0 +1,92 @@
+"""Tests for frontend/style.css — design tokens and dark theme."""
+
+import pathlib
+
+CSS_PATH = pathlib.Path(__file__).parent.parent.parent / "frontend" / "style.css"
+
+
+def read_css() -> str:
+    return CSS_PATH.read_text(encoding="utf-8")
+
+
+def test_css_design_tokens():
+    css = read_css()
+    assert "--bg:" in css
+    assert "--bell:" in css
+    assert "--font-mono:" in css
+    assert "--tile-height:" in css
+    assert "--t-zoom:" in css
+
+
+def test_css_session_grid(css=None):
+    css = read_css()
+    assert "auto-fill" in css
+    assert "minmax" in css
+
+
+def test_css_tile_height(css=None):
+    css = read_css()
+    assert ".session-tile" in css
+    assert "var(--tile-height)" in css
+
+
+def test_css_bell_indicator(css=None):
+    css = read_css()
+    assert "bell-pulse" in css
+    assert ".session-tile--bell" in css
+    assert ".tile-bell" in css
+
+
+def test_css_breakpoints():
+    css = read_css()
+    assert "599px" in css
+    assert "899px" in css
+
+
+def test_css_zoom_transition():
+    css = read_css()
+    assert ".session-tile--expanding" in css
+    assert "session-tile--expanded" in css
+    assert ".session-grid--dimming" in css
+
+
+def test_css_bell_count_and_toast():
+    css = read_css()
+    assert ".tile-bell-count" in css
+    assert ".connection-status--ok" in css
+    assert ".connection-status--warn" in css
+    assert ".connection-status--err" in css
+    assert ".toast" in css
+
+
+def test_css_mobile_tiers():
+    css = read_css()
+    assert "session-tile--tier-bell" in css
+    assert "session-tile--tier-active" in css
+    assert "session-tile--tier-idle" in css
+
+
+def test_css_command_palette():
+    css = read_css()
+    assert ".command-palette__dialog" in css
+    assert ".command-palette__input" in css
+    assert ".palette-item" in css
+    assert ".palette-item--selected" in css
+
+
+def test_css_bottom_sheet():
+    css = read_css()
+    assert ".bottom-sheet__panel" in css
+    assert ".bottom-sheet__handle" in css
+    assert ".sheet-item" in css
+
+
+def test_css_session_pill():
+    css = read_css()
+    assert ".session-pill" in css
+    assert ".session-pill__label" in css
+
+
+def test_css_reduced_motion():
+    css = read_css()
+    assert "prefers-reduced-motion" in css