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, 17 insertions, 0 deletions

diff --git a/src/audio/idct.cc b/src/audio/idct.cc
new file mode 100644
index 0000000..5d6bde0
--- /dev/null
+++ b/src/audio/idct.cc
@@ -0,0 +1,17 @@
+#include "dct.h"
+#include "util/math.h"
+#include <math.h>
+
+void idct_512(const float input[DCT_SIZE], float output[DCT_SIZE]) {
+  float scale_k0 = sqrtf(1.0f / DCT_SIZE);
+  float scale_kn = sqrtf(2.0f / DCT_SIZE);
+
+  for (int n = 0; n < DCT_SIZE; ++n) {
+    float sum = 0.0f;
+    for (int k = 0; k < DCT_SIZE; ++k) {
+      float scale = (k == 0) ? scale_k0 : scale_kn;
+      sum += scale * input[k] * cosf((PI / DCT_SIZE) * (n + 0.5f) * k);
+    }
+    output[n] = sum;
+  }
+}