Support --json output format for all commands

[engalar]

Problem

Current table-formatted output is optimized for human reading but inefficient for programmatic/AI consumption:

1. Truncation — Column values get truncated (...) when they exceed display width, requiring multiple follow-up queries to get full qualified names
2. Parsing overhead — Table borders (│, ─, ┼) waste tokens and require error-prone parsing
3. No machine-readable format — No way to pipe output into other tools reliably

Proposal

Add --json (or --format json) flag to all output commands:

./mxcli -p app.mpr -c "SHOW ENTITIES IN Sales" --json
./mxcli -p app.mpr -c "DESCRIBE MICROFLOW Sales.ACT_Save" --json
./mxcli -p app.mpr -c "SHOW STRUCTURE IN Sales DEPTH 2" --json

Benefits

• Eliminates truncation — JSON naturally includes full values
• Zero parsing cost for AI agents — structured data directly usable
• Composable — enables piping into jq, other tools, or batch processing scripts
• Backward compatible — table format remains the default

Suggested output example

{
  "command": "SHOW ENTITIES IN Sales",
  "results": [
    {"qualifiedName": "Sales.Customer", "persistent": true, "attributes": 5, "associations": 2},
    {"qualifiedName": "Sales.Order", "persistent": true, "attributes": 8, "associations": 3}
  ]
}

Priority

High — this is a force multiplier for all other improvements. Without structured output, every other enhancement still requires table parsing.