Add embedded terminal tabs

[ph10w]

Overview

The standard Open Command Prompt action now opens cmd.exe in an Explorer++ tab. The elevated action remains external, and Explorer++ falls back to the existing external command prompt when the terminal control or ConPTY is unavailable.

Architecture

• Hosts Microsoft's HwndTerminal control inside the tab content area and connects it to cmd.exe through ConPTY.
• Loads the version-pinned Microsoft.Terminal.Control.dll from the Explorer++ application directory without adding a hard startup dependency.
• Includes the DLL in the portable packages and MSI, with the corresponding third-party attribution.

Behavior

• Starts the terminal in the active folder and updates the tab title and tooltip after cd by handling the Windows Terminal OSC 9;9 working-directory sequence.
• Uses a dedicated static command-line tab icon with theme-specific 16, 24, 32, and 48 pixel resources.
• Uses Cascadia Mono with the centrally configured Explorer++ font size, including live updates for open terminal tabs.
• Provides a native vertical scrollbar and mouse-wheel scrolling for terminal scrollback.
• Sends Tab and Shift+Tab to the terminal for completion while retaining Ctrl+Tab for Explorer++ tab switching.
• Integrates terminal tabs with focus handling, layout updates, and taskbar previews.
• Opens .bat and .cmd files activated in Explorer++ in a new terminal tab and keeps the prompt open after completion.

Checks performed

• Built Explorer++ in Release|x64.
• Built TestExplorer++ in Release|x64.
• Passed all 70 related command-controller and tab tests.
• Opened an embedded HwndTerminalClass tab from the release executable and confirmed a clean process exit.
• Activated an isolated .cmd file from the Explorer++ file list and confirmed that it created a terminal tab and executed successfully.
• Attempted the complete 781-test suite: 744 passed; the remaining 37 are environment-dependent failures caused by denied test-registry access and the decimal separator.
• Validated the MSI XML and terminal DLL source path. A local MSI build was not possible because WiX Toolset 3.11 is not installed.