feat(canvas): multi-node selection with marquee, group drag, and bulk close

[Anton-Horn]

What

Canvas multi-selection:

• Marquee drag over empty canvas selects multiple nodes
• Dragging any selected node moves the whole group together (useGroupNodeDrag)
• A selection ring marks selected-but-not-active panes (distinct from the focus halo)
• Canvas mini-dock context menus collapse to a bulk "Close All" while a multi-selection is active (useMultiNodeSelection)

Also in here

• terminal: rebuild the shared WebGL glyph atlas across all live terminals on repaint, fixing scrambled glyphs in sibling terminals that share the atlas
• editor: reload the Monaco model when the file changes on disk externally (other editor, agent, git checkout), skipping while the buffer is dirty so unsaved edits are never clobbered
• canvas: select-tool trackpad two-finger scroll pans again (mouse wheel still zooms); freeze in-flight zoom/pan animations when anchoring a marquee so the box stays under the cursor
• node cleanup when a tab is moved out via "Move into New Window" leaves an empty node

Bumps version to 1.3.0.

Closes #363
Closes #364
Closes #365

[GHAFRI]

editor: reload the Monaco model when the file changes on disk externally (other editor, agent, git checkout), skipping while the buffer is dirty so unsaved edits are never clobbered

This issue not fixed in my use case, only solution I found to make it reload is to simply rename the file in the file explorer. Otherwise inside the canvas or opening the file in new window does not reload it. Force reload (Shift+CMD+R) does actually reload the md file but I would lose agent sessions which is not ideal