AXI P2: Slim list command output to minimal schema

[LarsEckart]

Problem

List commands currently dump the full API object for every item. This wastes tokens when an agent is just trying to orient.

Examples:

• datasets returns 8 fields per item: name, description, settings{delete_protected}, expand_json_depth, slug, regular_columns_count, last_written_at, created_at
• boards list includes the full panels[] array — nested objects with query IDs, SLO IDs, positions, etc. This can be very large.
• columns list returns all 7 fields including description, hidden, created_at, updated_at
• markers list returns all 9 fields including timestamps

For a list, an agent typically only needs enough to identify the item and decide what to do next.

Fix

Default list schemas:

• datasets: slug, name
• boards: id, name, type
• columns: id, key_name, type
• markers: id, message, type
• derived_columns: id, alias, expression

Full objects remain available via the get-* commands.

Optionally add a --fields flag for agents that need additional fields in bulk.

Reference

AXI Principle 2 — Minimal default schemas