Skill discovery crashes with ENAMETOOLONG on symlink cycles

Problem

When a skill discovery directory (e.g. ~/.agents/skills) resolves to a path inside a source skill collection, ln -s creates a self-referential symlink. OpenCode's skill scanner follows it recursively and crashes with ENAMETOOLONG.

This happens because scan() in packages/opencode/src/skill/index.ts passes symlink: true to glob (which maps to follow: true), and there is no cycle detection or depth limit.

Reproduction

# clone a skills repo
git clone git@github.com:example/skills.git && cd skills

# make the discovery dir point into the source collection
ln -s "$PWD/skills" ~/.agents/skills

# create a skill link -- ln follows the directory symlink and
# creates skills/foo/foo pointing at itself
ln -s "$PWD/skills/foo" ~/.agents/skills/foo

# start opencode -- glob follows the cycle until ENAMETOOLONG
opencode

Suggested fix

Any of these would work (in order of simplicity):

1. Add maxDepth to the glob call. Skill bundles are shallow (skills/<name>/SKILL.md), so a depth of 3-4 prevents infinite traversal without changing behavior.
2. Catch ENAMETOOLONG and ELOOP in the scan function and skip the path with a warning.
3. Track visited realpaths before descending into each directory.