Add agentic JSON output mode for AI agent integration

[danielsuguimoto]

Issue	N/A
🪲 Bug Fix	No
🧰 Improvement	Yes
🏆 Feature	Yes
📝 Refactor	No
❌ Removed	No
📖 Documentation	No
⚠️ Break Change	No

Description
Adds a global --output json flag that enables machine-readable JSON output across kool commands, making the CLI suitable for use by AI agents and automation tools. When JSON mode is active, commands emit structured payloads instead of human-readable tables or text, diagnostics route to stderr to keep stdout clean for data, and interactive prompts are automatically disabled.

Commands with JSON output:

• kool status: emits {"services":[...],"count":N} with service state, ports, and running status
• kool logs: emits JSON Lines format ({"service":"...","message":"..."}) with streaming support for --follow
• kool info: emits structured payload with kool/docker versions, binary paths, and environment variables (KOOL_API_TOKEN is redacted)
• kool run: script listing works in JSON mode; script-not-found errors emit structured JSON to stderr with suggestions field

The existing --json flag on kool run is now hidden but remains functional for backwards compatibility, unified under the global --output json flag.

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Notes

• --output json is a global flag that must be placed before the script name when using kool run
• Script output from kool run <script> remains raw (unstructured) as it passes through the underlying command output
• The legacy --json flag on kool run is hidden but still works for backwards compatibility
• All 306 tests pass with go vet clean