feat: add fresh user experience test to all three CI platforms

Simulates a real user's first install → use flow:
  mcpp new hello → cd hello → mcpp build → mcpp run
Runs in a clean temp directory with no pre-existing config.
Verifies the output contains "Hello from hello".

Author: Sunrisepeak

.github/workflows/ci-macos.yml

@@ -306,6 +306,20 @@ jobs:
           "$MCPP" toolchain default llvm@20.1.7
           bash tests/e2e/run_all.sh
 
+      - name: Fresh user experience (mcpp new → build → run)
+        run: |
+          MCPP=$(find target -path "*/bin/mcpp" | head -1)
+          MCPP=$(cd "$(dirname "$MCPP")" && pwd)/$(basename "$MCPP")
+          FRESH=$(mktemp -d)
+          cd "$FRESH"
+          "$MCPP" new hello
+          cd hello
+          "$MCPP" build
+          out=$("$MCPP" run 2>&1)
+          echo "$out"
+          echo "$out" | grep -q "Hello from hello" || { echo "FAIL: unexpected output"; exit 1; }
+          echo ":: Fresh user experience PASS"
+
       - name: Self-host smoke (freshly-built mcpp builds itself again)
         run: |
           MCPP=$(find target -path "*/bin/mcpp" | head -1)

.github/workflows/ci-windows.yml

@@ -100,6 +100,20 @@ jobs:
           "$MCPP_SELF" toolchain default llvm@20.1.7 2>/dev/null || true
           bash tests/e2e/run_all.sh
 
+      - name: Fresh user experience (mcpp new → build → run)
+        shell: bash
+        run: |
+          export MCPP_VENDORED_XLINGS="$XLINGS_BIN"
+          FRESH=$(mktemp -d)
+          cd "$FRESH"
+          "$MCPP_SELF" new hello
+          cd hello
+          "$MCPP_SELF" build
+          out=$("$MCPP_SELF" run 2>&1)
+          echo "$out"
+          echo "$out" | grep -q "Hello from hello" || { echo "FAIL: unexpected output"; exit 1; }
+          echo ":: Fresh user experience PASS"
+
       - name: Self-host smoke (freshly-built mcpp builds itself again)
         shell: bash
         run: |

.github/workflows/ci.yml

@@ -128,6 +128,19 @@ jobs:
           "$MCPP" toolchain default gcc@16.1.0
           bash tests/e2e/run_all.sh
 
+      - name: Fresh user experience (mcpp new → build → run)
+        run: |
+          MCPP=$(realpath "$(find target -type f -name mcpp -printf '%T@ %p\n' | sort -rn | head -1 | cut -d' ' -f2)")
+          FRESH=$(mktemp -d)
+          cd "$FRESH"
+          "$MCPP" new hello
+          cd hello
+          "$MCPP" build
+          out=$("$MCPP" run 2>&1)
+          echo "$out"
+          echo "$out" | grep -q "Hello from hello" || { echo "FAIL: unexpected output"; exit 1; }
+          echo ":: Fresh user experience PASS"
+
       - name: Self-host smoke (freshly-built mcpp builds itself again)
         run: |
           MCPP=$(realpath "$(find target -type f -name mcpp -printf '%T@ %p\n' | sort -rn | head -1 | cut -d' ' -f2)")