Migrate benchmark workflow from BenchmarkCI to AirspeedVelocity (#48)

Replaces the manual BenchmarkCI workflow (50+ lines) with the modern
AirspeedVelocity action (3 lines).

Changes:
- Replaced benchmark.yml with AirspeedVelocity action
- Deleted benchmark-comment.yml (no longer needed)

Benefits:
- Much simpler and easier to maintain
- Consistent with other repos in the organization
- Automatic PR comments with benchmark results
- Better integration with GitHub Actions

The AirspeedVelocity action handles all the complexity internally:
- Running benchmarks on base and PR branches
- Comparing results and generating reports
- Posting formatted comments to PRs

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Stefan Krastanov <stefan@krastanov.org>
Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: 3 people

.github/workflows/benchmark-comment.yml

@@ -1,57 +1,22 @@
-name: Performance tracking
+name: Benchmarks
 on:
-  pull_request:
+  pull_request_target:
+    branches: [master, main]
+permissions:
+  pull-requests: write
 
-env:
-  PYTHON: ~
+concurrency:
+  # group by workflow and ref; the last slightly strange component ensures that for pull
+  # requests, we limit to 1 concurrent job, but for the master branch we don't
+  group: ${{ github.workflow }}-${{ github.ref }}-${{ (github.ref != 'refs/heads/master' && github.ref != 'refs/heads/main') || github.run_number }}
+  # Cancel intermediate builds, but only if it is a pull request build.
+  cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
 
 jobs:
-  performance-tracking:
+  benchmark:
     runs-on: ubuntu-latest
-    #runs-on: self-hosted
     steps:
-      # setup
-      - uses: actions/checkout@v5
-      - uses: julia-actions/setup-julia@latest
+      - uses: MilesCranmer/AirspeedVelocity.jl@action-v1
         with:
-          version: '1.10'
-      - uses: julia-actions/julia-buildpkg@latest
-      - name: install dependencies
-        run: julia -e 'using Pkg; pkg"add PkgBenchmark BenchmarkCI@0.1"'
-
-      # run the benchmark suite
-      - name: run benchmarks
-        run: |
-          julia -e '
-            using BenchmarkCI
-            BenchmarkCI.judge()
-            BenchmarkCI.displayjudgement()
-            '
-
-      # generate and record the benchmark result as markdown
-      - name: generate benchmark result
-        run: |
-          body=$(julia -e '
-          using BenchmarkCI
-
-          let
-              judgement = BenchmarkCI._loadjudge(BenchmarkCI.DEFAULT_WORKSPACE)
-              title = "Benchmark Result"
-              ciresult = BenchmarkCI.CIResult(; judgement, title)
-              BenchmarkCI.printcommentmd(stdout::IO, ciresult)
-          end
-          ')
-          body="${body//'%'/'%25'}"
-          body="${body//$'\n'/'%0A'}"
-          body="${body//$'\r'/'%0D'}"
-          echo $body > ./benchmark-result.artifact
-
-      # record the pull request number
-      - name: record pull request number
-        run: echo ${{ github.event.pull_request.number }} > ./pull-request-number.artifact
-
-      # save as artifacts (performance tracking (comment) workflow will use it)
-      - uses: actions/upload-artifact@v4
-        with:
-          name: performance-tracking
-          path: ./*.artifact
+          julia-version: '1'
+          tune: 'false'