ci: add Go version matrix and staticcheck job

- test job: run on Go 1.24.x (go.mod minimum), 1.25.x, 1.26.x. Catches
  stdlib behavior drift earlier than a single-version run. fail-fast
  off so a single version's failure does not mask other versions.
- staticcheck job: pinned to go.mod version, runs honnef.co/go/tools
  across the module. Catches unused params, redundant conversions, and
  suspicious patterns that go vet ignores. Currently clean.

bench-compare job left unchanged (still PR-only, informational).

Author: miclle

.github/workflows/ci.yml

@@ -11,17 +11,24 @@ permissions:
 
 jobs:
   test:
-    name: Go tests
+    name: Go tests (${{ matrix.go }})
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        # Cover the version pinned by go.mod and the two newer stable
+        # releases. Drop or bump as new Go versions ship; never go below
+        # the go.mod minimum.
+        go: ['1.24.x', '1.25.x', '1.26.x']
 
     steps:
       - name: Check out repository
         uses: actions/checkout@v5
 
-      - name: Set up Go
+      - name: Set up Go ${{ matrix.go }}
         uses: actions/setup-go@v6
         with:
-          go-version-file: go.mod
+          go-version: ${{ matrix.go }}
           cache-dependency-path: go.sum
 
       - name: Run default tests
@@ -33,6 +40,31 @@ jobs:
       - name: Run compatibility fixtures
         run: make compat-test
 
+  staticcheck:
+    name: staticcheck
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v5
+
+      - name: Set up Go
+        uses: actions/setup-go@v6
+        with:
+          go-version-file: go.mod
+          cache-dependency-path: go.sum
+
+      # Run honnef.co/go/tools/cmd/staticcheck against the whole module.
+      # staticcheck catches issues vet doesn't (unused params, redundant
+      # type conversions, dead code, suspicious patterns) and is the de
+      # facto Go linter beyond go vet.
+      - name: Install staticcheck
+        run: go install honnef.co/go/tools/cmd/staticcheck@latest
+
+      - name: Run staticcheck
+        run: $(go env GOPATH)/bin/staticcheck ./...
+
+
   fuzz:
     name: Fuzz smoke
     runs-on: ubuntu-latest