fix(effect): improve ReShade texture compatibility

[kakra]

Summary

Improve compatibility with ReShade effects that rely on initialized internal textures, mipmaps, sRGB texture semantics, and accurate back-buffer metadata.

The implementation aligns vkShade's Vulkan resources more closely with the resource and preprocessor behavior expected by ReShade effects.

Internal textures and mipmaps

Resolve file-backed texture metadata before allocating Vulkan resources and clean up partially constructed images if initialization fails.

Persistent internal textures are initialized before their first use so effects can safely sample temporal history or other resources that have not yet been written.

Allocate the mip levels declared by effects and regenerate their mip chains after writing passes when requested by the effect. File-backed textures receive the same mipmap handling after upload.

Linear and sRGB views

Create compatible linear and sRGB image views where Vulkan permits them.

Sampling, render-target attachment selection, and pipeline formats follow the effect's declared sRGB semantics. This allows effects to distinguish correctly between linear resource access and sRGB conversion without duplicating the underlying image.

Back-buffer metadata

Build on the upstream bit-depth and color-space support introduced by #113.

Replace the limited bit-depth helper with a ReShade-compatible mapping that covers additional packed, floating-point, and high-precision Vulkan formats. Unknown or unsupported formats use the corresponding ReShade fallback instead of being treated as conventional 8-bit or 16-bit back buffers.

Also provide BUFFER_COLOR_FORMAT using ReShade API format values rather than raw Vulkan enums. Linear and sRGB Vulkan variants are normalized to the corresponding typed ReShade format.

The bit-depth and color-format mappings are kept in a focused metadata helper with unit coverage for the supported formats.

Validation

• Release build succeeds.
• git diff --check is clean.
• All seven unit tests pass.
• Buffer bit-depth and color-space mappings have focused unit coverage.
• The complete local queue was previously smoke-tested with Euro Truck Simulator 2 under Proton.
• Deband.fx loads with the expected back-buffer metadata.

[kakra]

On hold until mipmap/color depth surfaced in the main branch.

[kakra]

Rebased the series onto the current main, which now includes #113 and its fix for #107. The branch now builds on that upstream implementation by extending the ReShade-compatible bit-depth mapping and adding BUFFER_COLOR_FORMAT with focused unit coverage. The texture initialization, mipmap, and sRGB-view work remains unchanged. The refreshed branch builds cleanly and all seven tests pass.