fix: three mobile/WSL bugs reported by tester

- Mobile idle tiles: display:none → height:36px so session content is
  visible (all sessions are 'idle' with zero bells — was blank on iPhone)
- .tile-pre dead CSS: merge font/color rules into .tile-body pre (the
  actual HTML selector) so snapshot text renders with monospace + muted
  color; update mobile active-tier selector to match
- systemd PATH: strip /mnt/ entries from PATH before writing service
  unit file — WSL paths with spaces caused systemd to reject the line

muxplex/cli.py

@@ -25,6 +25,10 @@ def install_service(*, system: bool = False) -> None:
     """Install muxplex as a systemd service."""
     executable = sys.executable
 
+    _raw_path = os.environ.get("PATH", "/usr/local/bin:/usr/bin:/bin")
+    _safe_path = ":".join(p for p in _raw_path.split(":") if not p.startswith("/mnt/"))
+    _safe_path = _safe_path or "/usr/local/bin:/usr/bin:/bin"
+
     unit = f"""\
 [Unit]
 Description=muxplex — web-based tmux session dashboard
@@ -35,7 +39,7 @@ Type=simple
 ExecStart={executable} -m muxplex
 Restart=on-failure
 RestartSec=5s
-Environment=PATH={os.environ.get("PATH", "/usr/local/bin:/usr/bin:/bin")}
+Environment=PATH={_safe_path}
 
 [Install]
 WantedBy={"multi-user.target" if system else "default.target"}

muxplex/frontend/style.css

@@ -228,6 +228,13 @@ body {
   bottom: 0;
   left: 0;
   right: 0;
+  padding: 6px 8px;
+  font-family: var(--font-mono);
+  font-size: 11px;
+  color: var(--text-dim);
+  white-space: pre;
+  overflow: hidden;
+  margin: 0;
 }
 
 .tile-pre {
@@ -678,15 +685,15 @@ body {
   .session-tile--tier-active {
     min-height: 60px;
   }
-  .session-tile--tier-active .tile-pre {
+  .session-tile--tier-active .tile-body pre {
     white-space: nowrap;
     overflow: hidden;
     text-overflow: ellipsis;
   }
 
-  /* Tier 3 — idle: name-only (~44px total) */
+  /* Tier 3 — idle: compact preview (36px body) */
   .session-tile--tier-idle .tile-body {
-    display: none;
+    height: 36px;
   }
   .session-tile--tier-idle {
     min-height: 44px;

muxplex/tests/test_cli.py

@@ -84,6 +84,43 @@ def test_install_service_system_mode_target(tmp_path, monkeypatch):
     assert "multi-user.target" in content
 
 
+def test_install_service_strips_wsl_mnt_paths_from_environment(tmp_path, monkeypatch):
+    """Fix 3: install_service() must strip /mnt/ paths from Environment=PATH.
+
+    WSL mounts Windows at /mnt/c/, /mnt/d/ etc.  Paths like
+    '/mnt/c/Program Files/dotnet/' contain spaces, causing systemd to
+    truncate and reject the Environment= line.
+    """
+    from muxplex.cli import install_service
+
+    fake_home = tmp_path / "home"
+    fake_home.mkdir()
+    monkeypatch.setattr(Path, "home", staticmethod(lambda: fake_home))
+
+    wsl_path = (
+        "/usr/local/bin:/usr/bin:/bin:/mnt/c/Program Files/dotnet:/mnt/d/tools/bin"
+    )
+    monkeypatch.setenv("PATH", wsl_path)
+
+    install_service(system=False)
+
+    unit_path = fake_home / ".config" / "systemd" / "user" / "muxplex.service"
+    content = unit_path.read_text()
+
+    # Find the Environment=PATH line
+    env_line = next(
+        (line for line in content.splitlines() if line.startswith("Environment=PATH=")),
+        None,
+    )
+    assert env_line is not None, "Environment=PATH line must be present"
+    assert "/mnt/" not in env_line, (
+        f"WSL /mnt/ paths must be stripped from Environment=PATH; got: {env_line!r}"
+    )
+    # Safe paths must still be present
+    assert "/usr/local/bin" in env_line
+    assert "/usr/bin" in env_line
+
+
 def test_dunder_main_calls_main():
     """python -m muxplex must call cli.main()."""
     import importlib.util

muxplex/tests/test_frontend_css.py

@@ -534,3 +534,56 @@ def test_css_reduced_motion_sidebar_after_toast():
     assert toast_idx < sidebar_idx, (
         ".session-sidebar must come after .toast in reduced-motion block"
     )
+
+
+# ── Bug-fix regression tests ─────────────────────────────────────────────────
+
+
+def test_idle_tile_body_not_display_none():
+    """Fix 1: .session-tile--tier-idle .tile-body must NOT use display:none.
+
+    All sessions are 'idle' when zero bell notifications — display:none caused
+    a blank screen on mobile (iPhone).
+    """
+    css = read_css()
+    # Locate the idle rule block
+    marker = ".session-tile--tier-idle .tile-body"
+    assert marker in css, "idle .tile-body rule must exist"
+    idx = css.index(marker)
+    block_start = css.index("{", idx)
+    block_end = css.index("}", block_start)
+    block = css[block_start:block_end]
+    assert "display: none" not in block, (
+        ".session-tile--tier-idle .tile-body must not use display:none "
+        "(hides all tile content on mobile)"
+    )
+
+
+def test_tile_body_pre_has_typography():
+    """Fix 2a: .tile-body pre must carry font-family and color declarations.
+
+    Previously those rules were on dead .tile-pre class which was never in HTML.
+    """
+    css = read_css()
+    marker = ".tile-body pre"
+    assert marker in css, ".tile-body pre rule must exist"
+    idx = css.index(marker)
+    block_start = css.index("{", idx)
+    block_end = css.index("}", block_start)
+    block = css[block_start:block_end]
+    assert "font-family" in block, ".tile-body pre must declare font-family"
+    assert "color" in block, ".tile-body pre must declare color"
+
+
+def test_mobile_active_tier_targets_tile_body_pre_not_tile_pre():
+    """Fix 2b: mobile active-tier selector must be .tile-body pre, not .tile-pre.
+
+    .tile-pre is never applied in HTML; the real element is <pre> inside .tile-body.
+    """
+    css = read_css()
+    assert ".session-tile--tier-active .tile-body pre" in css, (
+        "mobile active-tier must target .tile-body pre"
+    )
+    assert ".session-tile--tier-active .tile-pre" not in css, (
+        ".tile-pre is a dead class — selector must be removed"
+    )