Change Command History shortcut from ⌘H to ⇧⌘H

⌘H is reserved by macOS for "Hide Application" and pre-empts app-level
menu bindings before they ever fire, so the Command History shortcut
never actually worked. Moved to ⇧⌘H and updated all references (in-app
help, macOS Help Book, README).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -21,7 +21,7 @@ A powerful native macOS AI chat application with support for multiple providers,
 - **Reasoning / Thinking Tokens** - Stream live reasoning from thinking-capable models (DeepSeek R1, Claude 3.7+, o1/o3, Qwen); configurable effort level (High/Medium/Low/Minimal); collapsible block auto-expands while thinking and collapses when the answer arrives
 - **Online Mode** - DuckDuckGo and Google web search integration
 - **Session Statistics** - Track token usage, costs, and response times
-- **Command History** - Navigate previous commands with searchable modal (⌘H)
+- **Command History** - Navigate previous commands with searchable modal (⇧⌘H)
 
 ### 🧠 Enhanced Memory & Context System
 - **Smart Context Selection** - Automatically select relevant messages to reduce token usage by 50-80%
@@ -193,7 +193,7 @@ Add your API keys in Settings (⌘,) → General tab:
 - `/load` or `/list` - List and load saved conversations (⌘L)
 - `/delete <name>` - Delete a saved conversation
 - `/export <md|json> [filename]` - Export conversation
-- `/history` - Open command history modal (⌘H)
+- `/history` - Open command history modal (⇧⌘H)
 
 ### Provider & Settings
 - `/provider [name]` - Switch or display current provider
@@ -238,7 +238,7 @@ Can you review this code? @~/project/main.swift
 - `⌘,` - Open settings
 - `⌘N` - New conversation
 - `⌘L` - List saved conversations
-- `⌘H` - Command history
+- `⇧⌘H` - Command history
 - `Esc` - Cancel generation / Close dropdown
 - `↑/↓` - Navigate command dropdown (when typing `/`)
 - `Return` - Send message