=== Task 15: Slimmed opencode.nix ===
Removed: agentsInput, externalSkills options; agents.json embedding; skills/context/commands/prompts symlinks
Kept: ohMyOpencodeSettings, extraSettings, extraPlugins, theme/formatter/plugin config

PASS: agentsInput removed
PASS: externalSkills removed
PASS: ohMyOpencodeSettings preserved
