Fix fork PR sccache failures with token-gated install and build retry #405

Job	Run time
Start gate (abort window)	4s
Build WebUI assets (shared)	1m 4s
Test (vmlens interleavings)	1m 4s
Code style (spotless) + package graph	49s
C++ Tests Ubuntu Latest x86_64	1m 6s
Cross-Compile manylinux2014 x86_64	1s
Build and Test Windows 2025 x86 (VS 2026)	1s
Build and Test Windows 2025 x86 (Ninja Multi-Config + sccache, eval)	1s
Build and Test macOS 15 arm64 (no Metal)	1s
Build and Test macOS 14 arm64 (Metal)	1s
Cross-Compile Android aarch64	1s
Build and Test Windows 2025 x86_64 (VS 2026)	1s
Cross-Compile manylinux_2_28 x86_64 (CUDA)	1s
Build and Test macOS 15 arm64 (Metal)	1s
Build and Test Linux aarch64	1s
Cross-Compile Android aarch64 (OpenCL/Adreno)	1s
Build and Test Windows 2025 x86_64 (Ninja Multi-Config + sccache, eval)	1s
Java Tests Ubuntu Latest x86_64	1s
Java Tests Windows 2025 x86_64 (VS 2026)	1s
Java Tests macOS 15 arm64 (no Metal)	1s
Java Tests Windows 2025 x86_64 (Ninja, eval)	1s
Java Tests macOS 15 arm64 (Metal)	1s
Java Tests macOS 14 arm64 (Metal)	1s
Package JARs	1s
Report	1s
Check: main branch / SNAPSHOT	1s
Check: v* tag	1s
Publish Snapshot to Central	1s
Publish Release to Central	1s
Attach Signed Binaries to GitHub Release	1s
Update Snapshot Pre-release on GitHub	1s
	4m 33s

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