cmm: color pipeline preparations

[mahkoh]

No description provided.

[Copilot]

Pull request overview

This PR prepares the color-management pipeline by making “no-op / embeddable” decisions render-intent-aware, and by adding infrastructure to reason about whether a target gamut/luminance is contained in a source description.

Changes:

• Thread RenderIntent into ColorDescription::embeds_into / LinearColorDescription::embeds_into checks and update call sites (Vulkan renderer, scanout path).
• Add cached LinearColorDescription::target_contained_in_primary() and supporting triangle containment algorithm.
• Extend CMM tests to cover target containment behavior and add a ColorMatrix::IDENTITY constant.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/gfx_apis/vulkan/renderer.rs	Updates embed checks to pass an explicit render intent for blend-buffer elision and color-transform caching.
src/gfx_api.rs	Makes direct-scanout eligibility checks intent-aware via embeds_into(..., ct.render_intent).
src/cmm/cmm_transform.rs	Adds a reusable identity matrix constant for future pipeline steps.
src/cmm/cmm_tests.rs	Adds tests validating target_contained_in_primary() across multiple primaries/luminance edge cases.
src/cmm/cmm_primaries.rs	Adds Primaries::about_equal() for approximate comparisons used by embed checks.
src/cmm/cmm_manager.rs	Initializes the new target_contained_in_primary cache field when creating descriptions.
src/cmm/cmm_luminance.rs	Refactors white-balance math helpers and adds Luminance::embeds_into(..., intent) for intent-aware identity checks.
src/cmm/cmm_description.rs	Adds cached target-containment computation and updates embed logic to use approximate primaries + luminance embedding.
algorithms/src/triangles.rs	Introduces a triangle containment helper used by the target-containment computation.
algorithms/src/lib.rs	Exposes the new triangles module from the algorithms crate.

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