Make paste keyboard shortcut customizable from Preferences

[da2r-20]

Summary

• Adds a paste entry to SHORTCUT_DEFAULTS under a new Editing category, surfacing it automatically in Preferences → Shortcuts. Defaults are platform-aware: Cmd+V on macOS, Ctrl+V on Windows, Ctrl+Shift+V on Linux (matches GNOME Terminal / Konsole convention so Ctrl+V next to Ctrl+C is not a footgun in shells).
• Routes paste through a single cross-platform pipeline: a main-process before-input-event listener matches the configured accelerator and tells the renderer to dispatch; the renderer routes by document.activeElement — terminal panes get bracketed-paste-aware PTY writes; native inputs delegate to webContents.paste() for proper cursor/undo/IME.
• Removes the hardcoded Windows Ctrl+V branch from terminal-utils.ts and the writeToPty argument from attachClipboardCopyHandler so paste no longer leaks into xterm key handlers.
• Edit menu shows the active binding label with registerAccelerator: false (label only, no double-firing); rebuilt on startup and on preferences-changed.

Architecture

New files:

• src/main/paste-accelerator.ts — owns accelerator state, parses Input events, installs the before-input-event listener (idempotent; resets on window close so macOS dock-reopen works).
• src/renderer/paste-dispatcher.ts — receives paste:dispatch, classifies focus, routes paste.

New IPC channels (preload paste namespace): paste:set-accelerator (renderer → main), paste:dispatch (main → renderer), paste:native (renderer → main).

Design doc: docs/superpowers/specs/2026-04-29-customizable-paste-shortcut-design.md
Plan: docs/superpowers/plans/2026-04-29-customizable-paste-shortcut.md

Test plan

Automated (passes on this branch):

• npm run build succeeds (main, preload, renderer)
• npm test — 1386 tests pass
• Unit tests added for matchesPasteAccelerator, the listener install lifecycle, the focus classifier, the bracketed-paste string builder, and per-platform paste defaults

Manual smoke test (Linux, completed):

• Default Ctrl+Shift+V pastes into a session terminal with bracketed paste
• Default Ctrl+Shift+V pastes into a board task-modal text input (cursor + undo correct)
• Rebound Ctrl+V works in both terminal and inputs; old Ctrl+Shift+V is suppressed
• Edit menu shows the active accelerator label (correct on startup too)
• Reset reverts behavior
• X11 middle-click primary-selection paste still works (regression)

Known follow-ups

• macOS / Windows verification deferred — implementer is on Linux. Design uses cross-platform primitives (before-input-event, webContents.paste()), but a macOS reviewer should re-verify Cmd+V default + dock-icon close-and-reopen (listener resets on window close), and a Windows reviewer should specifically check no double-paste in board task-modal inputs.
• Project-terminal panel paste path — the project shell terminal element doesn't carry the .terminal-pane class, so classifyTarget routes it as 'input' → webContents.paste() rather than the bracketed-paste path. Paste still works, but via a different codepath than session terminals. Adding the class would unify the two paths.