ci: add tests, benchmarks, and release automation workflows

[0xpantera]

Summary

• add ci-tests.yml to run monorepo package tests on PRs and pushes to master
• add benchmarks.yml to run benchmarks on schedule/manual dispatch and relevant master changes, then upload benchmark artifacts
• add release.yml to automate gh release create --generate-notes on tag pushes (v*)

Details

• test matrix uses Julia 1.11 and 1.12 on ubuntu-latest
• benchmark workflow runs:
  • julia --project=. benchmarks/run.jl
  • julia --project=. benchmarks/plot.jl
  • uploads latest benchmarks/artifacts/<timestamp> directory
• release workflow is idempotent on reruns (skips if the release already exists)

Why

This adds the core CI lanes for correctness (tests), performance observability (benchmarks), and release automation for tags.