Add embedded terminal tabs

[ph10w]

Overview

The standard Open Command Prompt action now opens cmd.exe in an Explorer++ tab. Elevated terminals remain external, with the existing command prompt used as a fallback when the embedded terminal is unavailable. Activating .bat or .cmd files opens a temporary terminal tab that closes when the script finishes.

Architecture

• Embeds Microsoft's HwndTerminal control and connects it to cmd.exe through ConPTY.
• Keeps terminal creation, process hosting, launch routing, message handling, clipboard access, and output parsing in focused terminal classes, minimizing changes to existing Explorer++ components.
• Loads the pinned Microsoft.Terminal.Control.dll dynamically from the application directory and includes it in portable and MSI packages with attribution.
• Defers ConPTY startup until the tab is visible and marshals terminal output to the UI thread, preserving the initial prompt when a terminal is reopened after exit.

Behavior

• Starts in the active folder, tracks cd changes in the tab title and tooltip, and closes interactive tabs when their command process exits.
• Supports terminal text copy and paste with surrounding control/whitespace cleanup, while preserving normal Explorer++ shortcuts outside terminal tabs.
• Provides Tab completion, Ctrl+Tab tab switching, scrollback with scrollbar and mouse wheel, Explorer++ font-size updates with Cascadia Mono, and a dedicated multi-size command-line icon.
• Integrates terminal content with tab focus, layout, taskbar previews, and safe initialization failure handling.

Checks performed

• Built Explorer++ and TestExplorer++ in Release|x64 with 0 warnings and 0 errors.
• Passed all 795 tests, including terminal clipboard/output parsing and locale-aware formatting coverage.
• Repeatedly verified open → exit → reopen, confirming that the path prompt appears immediately and remains usable.
• Verified interactive terminals, automatic batch execution/closure, and MSI XML/DLL paths. A local MSI build was not possible because WiX Toolset 3.11 is not installed.

[derceg]

Hi ph10w, this looks like a more significant change, so I appreciate the work you've put into it. I think it needs some justification, though. Is there a particular reason why running a terminal embedded in a tab is better than running it externally? Also, is Microsoft.Terminal.Control.dll designed to be used as a sort of public API in this way?

[ph10w]

Hi David,
My main use case is running small scripts while working in Explorer++. Opening them in an embedded terminal tab keeps the workflow within the current window and avoids covering limited monitor space with another window. On my system, an embedded terminal also opens noticeably faster than an external Windows Terminal instance.
This is not intended to replace external terminals. Users can still configure an Application Toolbar button to launch Windows Terminal whenever that is more appropriate.
Regarding Microsoft.Terminal.Control.dll: the Windows Terminal README describes the terminal core as “a reusable UI control that others can incorporate into their own applications.” The DLL also deliberately exports a flat C ABI, including functions such as CreateTerminal.
However, as far as I can tell, Microsoft does not document or guarantee this ABI as a stable, supported public API. This PR therefore uses a pinned DLL from an official Windows Terminal release, loads it dynamically, verifies all required exports, and disables the integration if the DLL is missing or incompatible. The implementation is based on the HwndTerminal implementation in the Windows Terminal repository.