feat(stdlib): add colorsys module — color space conversions

[Copilot]

Adds a colorsys module implementing RGB↔HSV, RGB↔HLS, and RGB↔YIQ conversions, matching Python's colorsys API exactly (float values in [0.0, 1.0], hue as fraction not degrees).

import colorsys

h, s, v = colorsys.rgb_to_hsv(0.2, 0.4, 0.6)
r, g, b = colorsys.hsv_to_rgb(h, s, v)

Changes

• New module: src/Sharpy.Stdlib/Colorsys/ with __Init__.cs, Colorsys.cs (6 pure functions, ~200 LOC)
• Spy source: src/Sharpy.Stdlib/spy/colorsys_module.spy
• Per-module csproj: modules/Sharpy.Stdlib.Colorsys.csproj
• Compiler registration: Added colorsys → ColorsysModule to StdlibClassNameOverrides in RoslynEmitter.CompilationUnit.cs
• Test expectation: Added colorsys_module to NativeStdlibCompilationTests.ExpectedModules
• Integration test: stdlib_colorsys.spy covering all 6 functions, roundtrips, and edge cases (black, white, pure colors)
• Docs: docs/stdlib/colorsys.md

[Copilot]

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[antonsynd]

Superseded by consolidated implementation in ce6a757 on dev branch. Issue #758 closed.