fix: fresh user test uses real xlings install mcpp flow

  xlings remove mcpp
  xlings install mcpp
  mcpp new hello
  cd hello
  mcpp run

100% real user flow — xlings installs mcpp, mcpp auto-installs
toolchain, builds and runs. No manual cp, no env manipulation.

Author: Sunrisepeak

.github/workflows/ci-macos.yml

@@ -318,14 +318,8 @@ jobs:
 
       - name: Fresh user experience (xlings install mcpp → new → run)
         run: |
-          # Replace xlings mcpp with our self-hosted build
-          MCPP_SELF=$(find target -path "*/bin/mcpp" | head -1)
-          MCPP_SELF=$(cd "$(dirname "$MCPP_SELF")" && pwd)/$(basename "$MCPP_SELF")
           xlings remove mcpp -y 2>/dev/null || true
-          MCPP_BIN=$(which mcpp 2>/dev/null || echo "$HOME/.xlings/subos/default/bin/mcpp")
-          cp "$MCPP_SELF" "$MCPP_BIN"
-          chmod +x "$MCPP_BIN"
-
+          xlings install mcpp -y
           TMP=$(mktemp -d)
           cd "$TMP"
           mcpp new hello

.github/workflows/ci-windows.yml

@@ -111,12 +111,8 @@ jobs:
       - name: Fresh user experience (xlings install mcpp → new → run)
         shell: bash
         run: |
-          # Replace xlings mcpp with our self-hosted build, then test
-          # the real user flow: mcpp new hello && cd hello && mcpp run
           xlings.exe remove mcpp -y 2>/dev/null || true
-          MCPP_BIN=$(which mcpp.exe 2>/dev/null || echo "$USERPROFILE/.xlings/subos/default/bin/mcpp.exe")
-          cp "$MCPP_SELF" "$MCPP_BIN"
-
+          xlings.exe install mcpp -y
           TMP=$(mktemp -d)
           cd "$TMP"
           mcpp.exe new hello

.github/workflows/ci.yml

@@ -136,13 +136,8 @@ jobs:
 
       - name: Fresh user experience (xlings install mcpp → new → run)
         run: |
-          # Replace xlings mcpp with our self-hosted build
-          MCPP_SELF=$(realpath "$(find target -type f -name mcpp -printf '%T@ %p\n' | sort -rn | head -1 | cut -d' ' -f2)")
           xlings remove mcpp -y 2>/dev/null || true
-          MCPP_BIN=$(which mcpp 2>/dev/null || echo "$HOME/.xlings/subos/default/bin/mcpp")
-          cp "$MCPP_SELF" "$MCPP_BIN"
-          chmod +x "$MCPP_BIN"
-
+          xlings install mcpp -y
           TMP=$(mktemp -d)
           cd "$TMP"
           mcpp new hello