New src/mobile/ module renders a phone-style shell: top surface tabs
(Stage/Time/Nodes/Mixer/Tree), a single full-bleed hero pane reusing the
existing PaneInstance renderers, a resizable timeline ribbon (peek/half/full
snap tiers riding above the floor), and a fixed transport bar wired to the
audio controller (play/pause, timecode, project scrub).
Gated entirely on the LB_MOBILE_UI env var: when set, main() opens a
phone-aspect window and update() routes the central panel through
render_mobile_shell instead of render_layout_node, sharing the same
build_frame context and post-render drain. Desktop is unchanged when unset.
Tabs mirror the pane list; per the wireframe the Toolbar and Infopanel do
not become tabs (they become the omnibutton and inspector in later phases),
and the Nodes surface is a placeholder pending the focus/patch rework.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Skyler Lehmkuhl