feat(build): add animated texture mcmeta pipeline and frame strip packager (#55)

[BharathASL]

Description

Implements the headless animated texture .mcmeta pipeline and multi-frame animation strip compiler for Keyframe (Issue #55, Epic #40).

Key Highlights:

1. Multi-Frame Vertical Strip Assembly: Compiles multi-frame SVG directories (e.g. textures/water_still/) into vertical 1:N PNG strips ($W \times (N \cdot W)$) across all 5 resolution tiers using @resvg/resvg-js.
2. SVG Defs ID Collision Isolation: Strips XML prologs/DOCTYPES and prefixes per-frame <defs> element IDs (f${frameIdx}_${id}) and references (url(#...), href="#...") to prevent gradient/mask shadowing across animation frames.
3. Natural Numerical Sorting: Enforces numerical sorting (0.svg, 1.svg, 2.svg ... 10.svg) to prevent alphabetical ordering issues.
4. Metadata Discovery Ladder & Presets: Auto-detects companion <stem>.svg.mcmeta, <stem>.png.mcmeta, <stem>.mcmeta, or directory animation.json, with built-in preset fallbacks for water, lava, fire, prismarine, sea lanterns, campfires, and lanterns.
5. Backwards-Compatibility Alias Propagation: Replicates .png.mcmeta files alongside aliased textures (e.g., short_grass -> grass.png.mcmeta).
6. Automated Test Suite: Added 7 comprehensive unit/integration test suites executable via npm test.

Affected Assets

• tools/lib/animation-packager.mjs (new)
• tools/test-animation-packager.mjs (new)
• tools/build.mjs (modified)
• package.json (modified)

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Type of Change

• feat: New vector texture master, blockstate, or compiler capability
• fix: Tiling fix, palette correction, or bugfix
• docs: Documentation improvement
• chore / refactor: Maintenance, dependencies, or codebase cleanup

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Contributor Checklist

• Ran npm run build and npm run build:all locally and verified all 5 resolution tiers compile successfully.
• Verified that npm test runs and passes all 7/7 unit and integration tests.
• Commit message follows Conventional Commits format.
• Signed off with Developer Certificate of Origin (git commit -s).
• Branch is rebased cleanly onto latest main.
• Formatting complies with .editorconfig.

Closes #55