ci: bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/benchmark.yml

@@ -26,7 +26,7 @@ jobs:
     name: Run competitive suite + publish RESULTS.md
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install wrk
         run: |

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
         python-version: ["3.12", "3.13"]
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install uv
         uses: astral-sh/setup-uv@v4
@@ -47,7 +47,7 @@ jobs:
     name: Lint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install uv
         uses: astral-sh/setup-uv@v4
@@ -70,7 +70,7 @@ jobs:
     name: Type check
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install uv
         uses: astral-sh/setup-uv@v4
@@ -91,7 +91,7 @@ jobs:
     # pytest-memray supports Linux and macOS only — never run on Windows.
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install uv
         uses: astral-sh/setup-uv@v4
@@ -120,7 +120,7 @@ jobs:
     name: Performance Regression Gate
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           # Need history so the committed baseline JSON is available.
           fetch-depth: 0
@@ -160,7 +160,7 @@ jobs:
     runs-on: ubuntu-latest
     continue-on-error: true
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install uv
         uses: astral-sh/setup-uv@v4

.github/workflows/docs.yml

@@ -18,7 +18,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install uv
         uses: astral-sh/setup-uv@v4

.github/workflows/publish.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     environment: pypi
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install uv
         uses: astral-sh/setup-uv@v4

.github/workflows/security.yml

@@ -17,7 +17,7 @@ jobs:
     name: Bandit (SAST)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v5
         with:
           python-version: "3.13"
@@ -30,14 +30,14 @@ jobs:
     container:
       image: semgrep/semgrep
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - run: semgrep --config=p/python --config=p/security-audit --config=p/owasp-top-ten --error --severity ERROR --severity WARNING src/
 
   pip-audit:
     name: pip-audit (dependency CVEs)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v5
         with:
           python-version: "3.13"
@@ -50,7 +50,7 @@ jobs:
     name: Gitleaks (secrets)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       # Use the gitleaks CLI directly: the gitleaks-action requires a paid
@@ -68,7 +68,7 @@ jobs:
       actions: read
       contents: read
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: github/codeql-action/init@v3
         with:
           languages: python

.github/workflows/wheels.yml

@@ -34,7 +34,7 @@ jobs:
             archs: "AMD64"
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       # QEMU is required to cross-build Linux aarch64 wheels on x86_64 runners.
       - name: Set up QEMU
@@ -75,7 +75,7 @@ jobs:
     name: Build sdist
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install uv
         uses: astral-sh/setup-uv@v4