ci: add msrv compile guard for rust 1.75.0

Author: rexleimo

.github/workflows/ci.yml

@@ -177,6 +177,25 @@ jobs:
           cargo test -p rexos-tools --locked tests::web::fetch::web_fetch_respects_egress_policy_rules
           cargo test -p rexos-tools --locked tests::browser::policy::url::
 
+  msrv-compile:
+    name: msrv compile (rust 1.75.0)
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install Rust 1.75.0
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          toolchain: 1.75.0
+
+      - name: Rust cache
+        uses: Swatinem/rust-cache@v2
+
+      - name: Check (workspace, locked)
+        run: cargo check --workspace --locked
+
   docs:
     name: docs build
     runs-on: ubuntu-latest

scripts/tests/test_ci_workflows.py

@@ -29,6 +29,14 @@ def test_ci_includes_windows_security_boundaries_fast_slice(self):
         )
         self.assertIn("cargo test -p rexos-tools --locked tests::browser::policy::url::", ci)
 
+    def test_ci_includes_msrv_compile_guard(self):
+        ci = (REPO_ROOT / ".github/workflows/ci.yml").read_text(encoding="utf-8")
+        self.assertIn("msrv-compile", ci)
+        self.assertIn("msrv compile (rust 1.75.0)", ci)
+        self.assertIn("Install Rust 1.75.0", ci)
+        self.assertIn("toolchain: 1.75.0", ci)
+        self.assertIn("cargo check --workspace --locked", ci)
+
     def test_provider_nightly_workflow_generates_health_artifacts(self):
         workflow = (
             REPO_ROOT / ".github/workflows/provider-nightly.yml"