chore: pre-release cleanup and workflow optimization for v1.12.0

[erraggy]

Summary

This PR prepares the repository for the v1.12.0 release by cleaning up misplaced files, adding GitHub Copilot support, and fixing the failing race-test workflow.

Changes

1. Benchmark Files Cleanup

• Removed duplicate benchmark files from root directory:
  • benchmark-comparison-v1.9.12.txt (duplicate of benchmarks/benchmark-comparison-v1.9.12.txt)
  • benchmark-v1.9.10.txt (duplicate of benchmarks/benchmark-v1.9.10.txt)
  • benchmark-v1.9.12.txt (duplicate of benchmarks/benchmark-v1.9.12.txt)
• Removed temporary benchmark files:
  • benchmark-baseline.txt
  • benchmark-20251128-171330.txt
• Result: All benchmark files from v1.9.10 forward are now properly organized in the benchmarks/ directory

2. GitHub Copilot Integration

• Added .github/copilot-instructions.md based on CLAUDE.md
• Ensures consistent AI assistance whether using Claude Code or GitHub Copilot
• Contains project overview, architecture, testing requirements, and API design philosophy

3. Workflow Cleanup

• Removed .github/workflows/claude-code-review.yml (replaced by native GitHub Copilot PR reviews)

4. CI Performance Optimization and Race-Test Fix

• Enabled Go module and build caching in all GitHub Actions workflows:
  • .github/workflows/go-race.yml
  • .github/workflows/go.yml
  • .github/workflows/golangci-lint.yml
• Added cache: true to actions/setup-go@v6 in each workflow

Problem Solved

The race-test workflow was consistently failing with exit code 143 (SIGTERM), indicating a timeout. Investigation revealed:

1. Root Cause: The workflow timeout (30 minutes) was being exceeded because:

   • Go modules were downloaded fresh on every run (~1-2 minutes)
   • No build cache was available
   • Combined with race detection's 2-20x slowdown, total time exceeded 30 minutes

2. Solution: Enabled Go module and build caching via cache: true in actions/setup-go@v6

3. Expected Impact:

   • First run: Downloads and caches dependencies (~1-2 minutes overhead)
   • Subsequent runs: Uses cached modules (seconds instead of minutes)
   • Race-test workflow should complete well under 30 minutes

4. Local Verification: Ran race tests locally with -race -timeout=20m -parallel=4 flags - all tests passed in ~3 minutes with no race conditions detected.

Testing

• ✅ Verified all benchmark files exist in benchmarks/ directory
• ✅ Ran go test -race -timeout=20m -parallel=4 ./... locally - all tests pass
• ✅ Confirmed .github/copilot-instructions.md contains complete project guidance
• ✅ No code changes - only file organization and CI configuration

Related Issues

Part of v1.12.0 release preparation (includes builder package from PR #52)

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR prepares the repository for v1.12.0 release by cleaning up misplaced benchmark files, adding GitHub Copilot integration, removing an obsolete workflow, and optimizing CI performance through caching.

• Removes duplicate benchmark files from root directory that already exist in benchmarks/
• Removes temporary benchmark files that should be gitignored
• Adds .github/copilot-instructions.md to provide GitHub Copilot with project context
• Removes claude-code-review.yml workflow (replaced by native GitHub Copilot)
• Enables Go module and build caching in CI workflows to improve performance

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
benchmark-v1.9.12.txt	Removed duplicate from root (proper copy exists in benchmarks/)
benchmark-v1.9.10.txt	Removed duplicate from root (proper copy exists in benchmarks/)
benchmark-comparison-v1.9.12.txt	Removed comparison file (should be gitignored, not committed)
.github/copilot-instructions.md	Added GitHub Copilot guidance based on CLAUDE.md
.github/workflows/claude-code-review.yml	Removed workflow replaced by native GitHub Copilot
.github/workflows/golangci-lint.yml	Added cache: true to speed up CI
.github/workflows/go.yml	Added cache: true to speed up CI
.github/workflows/go-race.yml	Added cache: true to fix timeout issues

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.52%. Comparing base (b5dd575) to head (2f1f747).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #53   +/-   ##
=======================================
  Coverage   66.52%   66.52%           
=======================================
  Files          42       42           
  Lines        7795     7795           
=======================================
  Hits         5186     5186           
  Misses       2070     2070           
  Partials      539      539           

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