fix(installer): harden greenfield detector contracts

packages/mosaic/framework/tools/_scripts/mosaic-link-runtime-assets

@@ -68,8 +68,15 @@ copy_claude_settings_guarded() {
     guard_args+=(--allow-inactive-enforcement)
   fi
 
-  if command -v mosaic >/dev/null 2>&1; then
-    if mosaic "${guard_args[@]}"; then
+  local mosaic_cli="${MOSAIC_CLI_PATH:-}"
+  # Unified install passes P3's committed absolute artifact. Standalone
+  # framework installs may resolve PATH once, but still invoke the resulting
+  # absolute path rather than a bare command.
+  if [[ -z "$mosaic_cli" ]]; then
+    mosaic_cli="$(command -v mosaic 2>/dev/null || true)"
+  fi
+  if [[ "$mosaic_cli" == /* && -x "$mosaic_cli" ]]; then
+    if "$mosaic_cli" "${guard_args[@]}"; then
       return 0
     fi
     echo "[mosaic-link] Enforcement hooks were NOT wired into $dst (see message above)." >&2
@@ -77,7 +84,7 @@ copy_claude_settings_guarded() {
     return 0
   fi
 
-  echo "[mosaic-link] ERROR: 'mosaic' CLI not found on PATH — cannot confirm lease-enforcement" >&2
+  echo "[mosaic-link] ERROR: P3 absolute mosaic CLI unavailable — cannot confirm lease-enforcement" >&2
   echo "[mosaic-link] activation capability. enforcement requested but activation half absent —" >&2
   echo "[mosaic-link] needs a published CLI carrying launch-runtime activation + a broker" >&2
   echo "[mosaic-link] supervisor; refusing to wire a dead gate (see #869)." >&2