feat(terminal): add rename support for terminal tiles

[kolindes]

Adds the ability to rename terminal sessions from the terminal list panel (right sidebar). Custom names persist across restarts and sync with the tile title bar on the canvas.

How it works:

• Hover over a terminal entry in the list — a pencil icon (✎) appears
• Click the icon or double-click the terminal name to enter edit mode
• Type a new name, press Enter to save (or Escape to cancel)
• The tile title bar on the canvas updates immediately
• Names are stored in canvas-state.json as customName on each terminal tile

Files changed (7):

• canvas-persistence.ts — customName?: string added to TileState
• tile-manager.js — save/restore customName, new renameTerminal() method
• tile-renderer.js — getTileLabel() prioritizes customName for terminal tiles
• renderer.js — terminal-list:rename IPC handler, customName in list entries
• terminal-list/App.tsx — rename button, double-click edit, inline input
• terminal-list/App.css — .rename-btn and .rename-input styles
• universal.ts — terminal-list:renamed added to listener channels

Testing:

• Created terminal tiles, renamed via pencil button and double-click
• Verified name persists after app restart
• Verified tile title bar updates on canvas
• Verified empty name reverts to default (cwd/displayName)
• Verified Escape cancels edit without saving
• Build passes (bun run build)

[yiliush]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[kolindes]

I have read the Contributor License Agreement (CLA) and hereby sign the CLA.