Use C++ RAII for command line resource lifetime management

[solidpixel]

The current front-end wrapper uses manual resource lifetime management with new/delete, alloc/free, and open/close pairs. It has always leaked in error paths, which makes using ASAN for genuine leak detection harder, especially when combined with fuzz testing.

We should just use C++ RAII given that the front-end is not a performance critical part of the codec, and it makes the entire thing more maintainable.

Fixes #631

[Copilot]

Pull request overview

This PR refactors the CLI/front-end resource management to use C++ RAII (e.g., std::unique_ptr, std::vector, and stream-based file I/O) instead of manual new[]/delete[] and alloc/free pairs, with the goal of eliminating leaks in error paths and improving maintainability.

Changes:

• Introduces RAII wrappers for astcenc_context and astcenc_image, and propagates these types through CLI image load/store and top-level processing.
• Replaces raw compressed payload buffers (uint8_t* + length) with std::vector<uint8_t> in astc_compressed_image.
• Reworks several image container I/O paths (KTX/DDS and .astc) to use std::ifstream/std::ofstream and standard containers.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
Source/astcenccli_toplevel.cpp	Switches CLI pipeline to RAII-managed codec contexts and images; updates diagnostic and processing call sites.
Source/astcenccli_platform_dependents.cpp	Replaces manual new[]/delete[] for thread descriptors with std::vector.
Source/astcenccli_internal.h	Introduces RAII pointer aliases/deleters and updates API signatures to return smart pointers/vectors.
Source/astcenccli_image.cpp	Implements astcenc_image RAII allocation and deletion; converts float extraction to std::vector<float>.
Source/astcenccli_image_load_store.cpp	Converts multiple loaders/storers to RAII (vectors, smart buffers) and stream I/O; updates compressed image handling.
Source/astcenccli_image_external.cpp	Updates external PNG loader to return RAII-managed images.

Comments suppressed due to low confidence (1)

Source/astcenccli_image_load_store.cpp:2206

• In the 8-bit DDS writer, the per-slice base pointer offset uses dim_z instead of dim_x, which miscomputes the start of each Z-slice and will corrupt output (and can go out-of-bounds) for 3D images.

		for (unsigned int z = 1; z < dim_z; z++)
		{
			row_pointers8[z] = row_pointers8[0] + dim_y * z;
			row_pointers8[z][0] = row_pointers8[0][0] + dim_y * dim_z * image_components * z;
		}

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[Copilot]

Pull request overview

Copilot reviewed 20 out of 21 changed files in this pull request and generated 2 comments.