Feature: exclude/deny skills from the skill selector (not just from the model's context)

Summary

There's currently no way to keep specific skills out of the interactive skill selector
(/skills picker). permission.skill: { "gsd-*": "deny" } correctly removes denied skills from
the model's <available_skills> context, but those same skills still appear in the human-facing
selector. I'd like a config option to exclude skills from discovery/the picker as well.

Motivation

I use OpenCode alongside Claude Code on the same machine. Claude Code has ~70 plugin skills
installed under ~/.claude/skills/, which OpenCode also scans (Claude-compat discovery). In
OpenCode those skills are irrelevant, so:

• They clutter the /skills selector with dozens of entries I'll never use in OpenCode.
• I can't remove them from ~/.claude/skills/ because Claude Code needs them there.

permission.skill deny handles the context/token side nicely, but not the picker side.

Current behavior

• permission.skill: { "*": "allow", "gsd-*": "deny" } → denied skills are excluded from the
  model's available-skills list (good, expected). ✅
• The /skills selector still lists every discovered skill, including the denied ones. ❌
• The only skills.* config is skills.paths, which adds discovery locations — there's no
  corresponding exclude/ignore/disable option.

Proposed solutions (any one would work)

1. Have the selector honor permission.skill deny — the simplest: if a skill is denied for the
   active agent, omit it from the picker too. (One mental model for "hide this skill," both surfaces.)
2. A skills.exclude / skills.ignore glob list — complement to skills.paths:

   "skills": {
     "exclude": ["gsd-*", "adhd"]   // by name, or path glob
   }
   

3. A discovery-path opt-out — e.g. a way to disable the ~/.claude/skills Claude-compat scan
   specifically (parallels OPENCODE_DISABLE_CLAUDE_CODE_PROMPT for the global CLAUDE.md), or to
   set the scanned skill roots explicitly.

Environment

• OpenCode 1.18.14 (Homebrew, macOS arm64)
• Skills discovered from ~/.claude/skills (Claude Code plugins) in addition to project/OpenCode paths.

Workaround (for others hitting this)

The selector has a search box — typing a prefix (e.g. the skill family you want) filters it, so the
noise is avoidable in day-to-day use even though it can't be permanently hidden.