feat(keybinding): add keybindings for reasoning cycling and view switching

[akougkas]

Problem

Missing keybindings for frequently used toggles:

• Reasoning level (6 values: off/minimal/low/medium/high/xhigh) has no dedicated keybinding. It is auto-set by mode transitions (which users may not want) and accessible only via the display-only /reasoning command.
• View switching (editor/dispatch/dashboard) has no manual toggle. Views change only via auto-transitions on dispatch events or by typing /dashboard.

Available keys:
Per PAN-KEYBOARD-BINDINGS.md Part 5.4:

• ctrl+x is the only safe ctrl+letter key (no Pi binding, no terminal conflict)
• f1 through f12 are all free and work in all terminals
• alt+c through alt+z (most) are free but broken on legacy macOS

Audit Reference

AUDIT-ISSUES.md: D6, D7

Objective

Provide keybindings for the most common toggleable surfaces.

Deliverables

• Decide: assign f1 for reasoning cycling (or ctrl+x + r chord)
• Decide: assign f2 for view cycling (editor → dispatch → dashboard)
• Register via pi.registerShortcut()
• Add to /hotkeys display
• Document in PAN-KEYBOARD-BINDINGS.md