Without mode: subagent, all 68 agents default to mode: all and appear as
primary agents the user Tab-cycles through, making the UX unusable.
With mode: subagent they are invoked on-demand via @agent-name.
OpenCode only accepts hex color codes (e.g. #00FFFF), not named colors
(e.g. cyan). Add resolve_opencode_color() with a 14-entry lookup table
and wire it into convert_opencode(). Colors already in hex pass through.
OpenCode docs now specify agents/ (plural) as the standard directory name;
agent/ (singular) is legacy backwards-compat. Update the converter output
path, installer source/dest paths, and .gitignore entry accordingly.
