Rename directories to plural form: skill/ → skills/, agent/ → agents/, command/ → commands/

- Rename skill/ to skills/ for consistency with naming conventions
- Rename agent/ to agents/ and command/ to commands/
- Update AGENTS.md with all directory references
- Update scripts/test-skill.sh paths
- Update prompts/athena.txt documentation

This aligns with best practices of using plural directory names and updates
all documentation to reflect the new structure.

skills/research/SKILL.md

@@ -0,0 +1,54 @@
+---
+name: research
+description: "Research and investigation workflows. Use when: (1) researching technologies or tools, (2) investigating best practices, (3) comparing solutions, (4) gathering information for decisions, (5) deep-diving into topics. Triggers: research, investigate, explore, compare, learn about, what are best practices for, how does X work."
+compatibility: opencode
+---
+
+# Research
+
+Research and investigation workflows for informed decision-making.
+
+## Status: Stub
+
+This skill is a placeholder for future development. Core functionality to be added:
+
+## Planned Features
+
+### Investigation Workflow
+- Multi-source research (web, docs, code)
+- Source credibility assessment
+- Summary with drill-down capability
+
+### Technology Evaluation
+- Feature comparison matrices
+- Pros/cons analysis
+- Fit-for-purpose assessment
+
+### Best Practices Discovery
+- Industry standards lookup
+- Implementation patterns
+- Common pitfalls
+
+### Learning Path Generation
+- Topic breakdown
+- Resource recommendations
+- Progress tracking
+
+## Integration Points
+
+- **Anytype**: Save research findings to Resources
+- **Web Search**: Primary research source
+- **librarian agent**: External documentation lookup
+
+## Quick Commands (Future)
+
+| Command | Description |
+|---------|-------------|
+| `research [topic]` | Start research session |
+| `compare [A] vs [B]` | Feature comparison |
+| `best practices [topic]` | Lookup standards |
+| `learn [topic]` | Generate learning path |
+
+## Notes
+
+Expand this skill based on actual research patterns that emerge from usage.