Use the vanilla copper chest texture for copper chests

[rubensworks]

Copper colossal chests now render with Minecraft's own copper chest texture (the unoxidized one), like wooden chests already use the vanilla chest texture. CC2's custom textures/entity/chest/copper.png is removed.

• RenderChestCore.getMaterial returns Sheets.chooseSprite(COPPER_UNAFFECTED, SINGLE) for copper.
• TestChestTextures skips copper like wood, because the texture is no longer in CC2. I checked that the vanilla texture also satisfies the test's lid/base overlap rule, so it doesn't z-fight.
• Unchanged: the copper wall and core block textures, which come from CC1 and don't derive from the chest texture.

Testing

• ./gradlew build passes.
• Checked in a NeoForge dev client with clientdevbridge: a 4x4x4 copper colossal chest next to a vanilla copper chest, with matching textures and no missing-texture warnings in the log.

🤖 Generated with Claude Code

https://claude.ai/code/session_01RSz5r6eowhjNuANBjZE2v6

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Generated by Claude Code

[coveralls]

Coverage Report for CI Build 38076313404

Coverage decreased (-0.03%) to 77.291%

Details

• Coverage decreased (-0.03%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• 7 coverage regressions across 1 file.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

7 previously-covered lines in 1 file lost coverage.

File	Lines Losing Coverage	Coverage
org/cyclops/colossalchests2/client/render/RenderChestCore.java	7	26.4%

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Coverage Stats

Relevant Lines:	6902
Covered Lines:	5650
Line Coverage:	81.86%
Relevant Branches:	2843
Covered Branches:	1882
Branch Coverage:	66.2%
Branches in Coverage %:	Yes
Coverage Strength:	9.93 hits per line

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💛 - Coveralls