[Athena] Fix CI timeout: skip accuracy tests in short mode

[syifan]

Summary

• Add testing.Short() skip to all 5 accuracy tests in benchmarks/accuracy_test.go
• CI passes -short flag but these tests didn't check it, causing the Acceptance Tests job to timeout (>5min) on every push
• medium_test.go and polybench_test.go already had this pattern; accuracy_test.go was the only file missing it

Impact

This is the #1 CI blocker — every push to main fails because TestAccuracyAgainstBaseline runs 25+ full pipeline simulations. With this fix, CI should pass for the first time.

Test plan

• CI Acceptance Tests job completes within 5min timeout
• PRs [Leo] Fix README factual inaccuracies vs actual code (Issue #496) #507 and [Leo] Fix reproduce_experiments.py — use real simulation data (Issue #495) #500 (previously blocked by CI failure) can proceed

Tests affected

• TestAccuracyAgainstBaseline — skipped in short mode
• TestAccuracyDependencyChain — skipped in short mode
• TestAccuracyArithmetic — skipped in short mode
• TestAccuracyBranch — skipped in short mode
• TestGenerateAccuracyReport — skipped in short mode

These tests still run in the dedicated accuracy workflows (accuracy-report.yml, h5-accuracy-report.yml) which don't pass -short.

🤖 Generated with Claude Code

[github-actions]

Performance Regression Analysis

Performance Benchmark Comparison

Compares PR benchmarks against main branch baseline.
Benchmarks: pipeline tick throughput across ALU, memory, mixed workloads.

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*Automated benchmark comparison via `go test -bench` + benchstat*