chore: SHA-pin GitHub Actions for supply chain security

Pin all GitHub Actions to specific commit SHAs instead of mutable tags
to prevent supply chain attacks. Tags preserved as comments.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/quality.yml

@@ -15,7 +15,7 @@ jobs:
           find . -type f -perm /111 -name "*.sh" | head -10 || true
       
       - name: Check for secrets
-        uses: trufflesecurity/trufflehog@main
+        uses: trufflesecurity/trufflehog@7ee2e0fdffec27d19ccbb8fb3dcf8a83b9d7f9e8 # main
         with:
           path: ./
           base: ${{ github.event.pull_request.base.sha || github.event.before }}
@@ -32,7 +32,7 @@ jobs:
           find . -type f -size +1M -not -path "./.git/*" | head -10 || echo "No large files"
       
       - name: EditorConfig check
-        uses: editorconfig-checker/action-editorconfig-checker@main
+        uses: editorconfig-checker/action-editorconfig-checker@4054fa83a075fdf090bd098bdb1c09aaf64a4169 # main
         continue-on-error: true
 
   docs:

.github/workflows/rust-ci.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
-      - uses: dtolnay/rust-toolchain@stable
+      - uses: dtolnay/rust-toolchain@4be9e76fd7c4901c61fb841f559994984270fce7 # stable
         with:
           components: rustfmt, clippy
       - uses: Swatinem/rust-cache@779680da715d629ac1d338a641029a2f4372abb5 # v2
@@ -33,7 +33,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
-      - uses: dtolnay/rust-toolchain@stable
+      - uses: dtolnay/rust-toolchain@4be9e76fd7c4901c61fb841f559994984270fce7 # stable
       - name: Install cargo-audit
         run: cargo install cargo-audit
       - name: Security audit
@@ -45,7 +45,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
-      - uses: dtolnay/rust-toolchain@stable
+      - uses: dtolnay/rust-toolchain@4be9e76fd7c4901c61fb841f559994984270fce7 # stable
       - name: Install tarpaulin
         run: cargo install cargo-tarpaulin
       - name: Generate coverage