Add SDL2-native C tools menu app for R36S

[RedMist20]

Motivation

• Replace the dialog-based Tools Menu.sh with a native SDL2 GUI that better fits the R36S device and provides a cleaner user experience.
• Provide D-pad / joystick/button navigation and an in-app terminal output panel so users can run and inspect the same safe network/driver commands without leaving the GUI.
• Support numeric prompts (channel / txpower) inside the application and provide an explicit exit back to the terminal.

Description

• Add cprog/tools-menu-sdl2/tools-menu-sdl2.c, a full-screen (640×480) SDL2 + SDL_ttf C program implementing the original shell menu items, command templates, and an in-app terminal output panel that captures command output.
• Implement command execution by writing a temporary shell script and streaming its output back via popen into a scrollable right-hand “Terminal Output” pane using run_script_to_output / run_action.
• Add joystick / D-pad mapping and logic for navigation, A/B/X/Y button behavior, and a numeric input overlay for actions that require numeric values.
• Add cprog/tools-menu-sdl2/CMakeLists.txt (pkg-config for sdl2 + SDL2_ttf) and update README.md with build/run instructions and control mappings.

Testing

• Attempted configuration and build with cmake -S cprog/tools-menu-sdl2 -B cprog/tools-menu-sdl2/build && cmake --build cprog/tools-menu-sdl2/build, which failed in this environment because the sdl2 pkg-config package was not present.
• Ran gcc -fsyntax-only cprog/tools-menu-sdl2/tools-menu-sdl2.c, which failed due to missing SDL2 headers in the environment.
• No further automated tests were available in this environment; runtime verification should be performed on a system with SDL2/SDL2_ttf development packages installed.

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Codex Task

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Support multi-digit entry in channel prompt

Numeric editing is fixed-length (len = strlen(input_value) with cursor bounded to len - 1), and the channel prompt initializes to a single character ("6"), so users can only cycle one digit (0–9). This makes it impossible to set common multi-digit channels like 36/44/149, which is a functional regression from the prior tools menu behavior.

Useful? React with 👍 / 👎.

[chatgpt-codex-connector]

Handle keyboard input while numeric overlay is active

Keyboard handling is entirely skipped when input_mode is true, so if a user opens a numeric action via keyboard (Enter), they cannot edit digits, confirm, or cancel from the keyboard. On setups without a joystick (such as desktop environments used for local testing), choosing channel/txpower input leaves the app effectively stuck until the window is closed.

Useful? React with 👍 / 👎.