ci: add MSRV and feature matrix checks

.github/workflows/rust.yml

@@ -39,4 +39,39 @@ jobs:
         run: cargo doc --no-deps --all-features
 
       - name: Build
-        run: cargo build --verbose
+        run: cargo build --verbose
+
+      - name: Check (no-default-features)
+        run: cargo check --no-default-features
+
+      - name: Test (no-default-features)
+        run: cargo test --no-default-features
+
+      - name: Check (default features)
+        run: cargo check
+
+      - name: Test (default features)
+        run: cargo test
+
+  msrv:
+    name: MSRV (Rust 1.88)
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install Rust 1.88
+        uses: dtolnay/rust-toolchain@1.88
+
+      - name: Cache dependencies
+        uses: Swatinem/rust-cache@v2
+
+      - name: Remove incompatible lockfile
+        run: rm -f Cargo.lock
+
+      - name: Check
+        run: cargo check --all-features
+
+      - name: Test
+        run: cargo test --all-features

Cargo.toml

@@ -2,7 +2,7 @@
 name = "contextvm-sdk"
 version = "0.1.1"
 edition = "2021"
-rust-version = "1.70"
+rust-version = "1.88"
 description = "Rust SDK for the ContextVM protocol — MCP over Nostr"
 license = "MIT"
 readme = "README.md"
@@ -58,6 +58,10 @@ required-features = ["rmcp"]
 name = "native_echo_client"
 required-features = ["rmcp"]
 
+[[test]]
+name = "e2e_happy_path"
+required-features = ["rmcp", "test-utils"]
+
 [[test]]
 name = "transport_integration"
 required-features = ["test-utils"]