Review feedback on #4610: array-form skills was silently replacing the
default `skills/` scan when the manifest declared any explicit entries.
Per the Claude plugins reference "Path behavior rules"
(https://code.claude.com/docs/en/plugins-reference#path-behavior-rules):
- `skills` ADDS to the default `skills/` scan
- `commands` / `slash-commands` REPLACE the default `commands/` scan
`resolvePluginDir` now takes an explicit `includeFallback` flag. `loadSkills`
passes `true` (fallback + declared entries, deduped by resolved absolute
path so a manifest may still list `./skills` alongside extras without
double-load); `loadSlashCommands` passes `false` (replace semantic
preserved). Deduplication keeps the fallback first and declared entries
in manifest order.
Regression tests cover both semantics: skills-array merges with default
`skills/`; commands-array replaces default `commands/` so a stray
`commands/default.md` no longer loads once the manifest declares an
alternative — matching Claude's documented behavior.
roboomp
f276d80fc4