♻️ (scripts/mcp.sh): refactor merge-functions and recovery-functions …

…to improve compatibility and efficiency ♻️ (scripts/mcp.sh): handle Windows lack of process substitution by using temp files ♻️ (scripts/mcp.sh): use helper _merge_functions_output to avoid code duplication ♻️ (scripts/mcp.sh): optimize recovery-functions to avoid repeated jq calls and simplify flow