feat: Implement spectool & specview; refactor coding style; update docs

This commit introduces new tools for spectrogram manipulation and visualization, establishes a consistent coding style, and updates project documentation.

Key changes include:

- **Spectrogram Tools:

  - : A command-line utility for analyzing WAV/MP3 files into custom  spectrogram format and playing back these spectrograms via the synth engine.

  - : A command-line tool for visualizing  spectrogram files as ASCII art in the console.

- **Coding Style Enforcement:

  - Added a  configuration file enforcing LLVM-based style with 2-space indentation, no tabs, and an 80-column line limit.

  - Renamed all C++ source files from  to  for project consistency.

  - Applied automatic formatting using
exit across the entire codebase.

- **Documentation & Workflow:

  - Created  to define a commit policy requiring tests to pass before committing.

  - Updated  with instructions for building and using  and , and referenced .

  - Updated  and  to reflect the new tools, audio architecture decisions (real-time additive synthesis, double-buffering for dynamic updates, WAV/MP3 support), coding style, and development workflow.

- **Build System:

  - Modified  to:

    - Include new targets for  and  under the  option.

    - Update source file extensions to .

    - Add a new end-to-end test for  to the  suite.

1 files changed, 29 insertions, 0 deletions

diff --git a/HOWTO.md b/HOWTO.md
index d948e59..059a039 100644
--- a/HOWTO.md
+++ b/HOWTO.md
@@ -25,6 +25,8 @@ cmake --build build
 
 ## Testing
 
+**Commit Policy**: Always run tests before committing. Refer to `CONTRIBUTING.md` for details.
+
 To build and run the tests, you need to enable the `DEMO_BUILD_TESTS` option in CMake.
 
 Available test suites:
@@ -69,3 +71,30 @@ The executable will be located at `build/spectool`.
 ```bash
 ./build/spectool play path/to/input.spec
 ```
+
+### Spectrogram Viewer (`specview`)
+
+A command-line tool for visualizing spectrogram files in ASCII art.
+
+#### Building the Tool
+
+`specview` is built along with `spectool` when enabling `DEMO_BUILD_TOOLS`.
+
+```bash
+cmake -S . -B build -DDEMO_BUILD_TOOLS=ON
+cmake --build build
+```
+The executable will be located at `build/specview`.
+
+#### Usage
+
+**View a spectrogram file:**
+```bash
+./build/specview path/to/input.spec
+```
+
+## References and links
+
+drum-kit: https://drive.google.com/file/d/13tc7XjkMg-tigvje5qpp6XazK-VcOjoc/view
+(got from https://www.reddit.com/r/Drumkits/)
+