Fix MSYS2 python3 path issue: pipe files via cat instead of open()

MinGW python3 is a native Windows binary that doesn't understand
POSIX paths like /tmp/foo.json. Piping file content through cat
(which runs in MSYS2 bash and handles path translation) to python's
stdin avoids the issue entirely.

Fixes Windows smoke test 8a and soak baseline collection.

Author: DeusData

scripts/smoke-test.sh

@@ -523,8 +523,8 @@ printf '[existing_section]\nline_from_user = true\n' > "$FAKE_HOME/.codex/config
 # Run install
 HOME="$FAKE_HOME" PATH="$FAKE_HOME/.local/bin:$PATH" "$BINARY" install -y 2>&1 || true
 
-# Helper for JSON validation
-json_get() { python3 -c "import json,sys,os; f='$1'; d=json.load(open(f)) if os.path.isfile(f) else {}; print($2)" 2>/dev/null || echo ""; }
+# Helper for JSON validation (pipe file to python — avoids MSYS2 path translation issues)
+json_get() { cat "$1" 2>/dev/null | python3 -c "import json,sys; d=json.load(sys.stdin); print($2)" 2>/dev/null || echo ""; }
 
 # 8a: Claude Code MCP (new path) — correct command
 CMD=$(json_get "$FAKE_HOME/.claude.json" "d.get('mcpServers',{}).get('codebase-memory-mcp',{}).get('command','')")
@@ -1044,7 +1044,7 @@ if [ -n "${SMOKE_DOWNLOAD_URL:-}" ]; then
   echo "OK 14b: updated binary runs"
 
   # 14c: Verify agent config was refreshed (stale path replaced)
-  UPD_CMD=$(python3 -c "import json,sys,os; f='$UPDATE_HOME/.claude.json'; d=json.load(open(f)) if os.path.isfile(f) else {}; print(d.get('mcpServers',{}).get('codebase-memory-mcp',{}).get('command',''))" 2>/dev/null || echo "")
+  UPD_CMD=$(cat "$UPDATE_HOME/.claude.json" 2>/dev/null | python3 -c "import json,sys; d=json.load(sys.stdin); print(d.get('mcpServers',{}).get('codebase-memory-mcp',{}).get('command',''))" 2>/dev/null || echo "")
   if [ "$UPD_CMD" = "/old/stale/path" ]; then
     echo "FAIL 14c: agent config still has stale path after update"
     exit 1

scripts/soak-test.sh

@@ -269,8 +269,9 @@ collect_snapshot
 # Derive project name (same logic as cbm_project_name_from_path)
 PROJ_NAME=$(echo "$SOAK_PROJECT" | sed 's|^/||; s|/|-|g')
 
-BASELINE_RSS=$(python3 -c "import json; d=json.load(open('/tmp/cbm-diagnostics-${SERVER_PID}.json')); print(d.get('rss_bytes',0))" 2>/dev/null || echo "0")
-BASELINE_FDS=$(python3 -c "import json; d=json.load(open('/tmp/cbm-diagnostics-${SERVER_PID}.json')); print(d.get('fd_count',0))" 2>/dev/null || echo "0")
+DIAG_FILE="/tmp/cbm-diagnostics-${SERVER_PID}.json"
+BASELINE_RSS=$(cat "$DIAG_FILE" 2>/dev/null | python3 -c "import json,sys; d=json.load(sys.stdin); print(d.get('rss_bytes',0))" 2>/dev/null || echo "0")
+BASELINE_FDS=$(cat "$DIAG_FILE" 2>/dev/null | python3 -c "import json,sys; d=json.load(sys.stdin); print(d.get('fd_count',0))" 2>/dev/null || echo "0")
 echo "OK: baseline RSS=${BASELINE_RSS} FDs=${BASELINE_FDS}"
 
 # ── Phase 3: Compressed workload loop ────────────────────────────