chore: migrate from opencode to trellis 0.5.0-rc.6

- Remove legacy .opencode/ directory and configuration
- Update .trellis/ to v0.5.0-rc.6 structure
- Refactor scripts: modularize common/, remove multi_agent/
- Add new common modules: git.py, io.py, log.py, types.py, etc.
- Update workflow.md and AGENTS.md
- Archive completed migration tasks

.claude/skills/trellis-meta/references/customize-local/change-agents.md

@@ -0,0 +1,54 @@
+# Change Local Agents
+
+When the user wants to change `trellis-research`, `trellis-implement`, or `trellis-check` behavior, edit platform agent files in the user project.
+
+## Read These Files First
+
+1. Target platform agent directory
+2. `.trellis/workflow.md` Phase 2 / research routing
+3. Current task `prd.md`
+4. Current task `implement.jsonl` / `check.jsonl`
+5. Relevant hook or agent prelude
+
+## Common Paths
+
+| Platform | Path |
+| --- | --- |
+| Claude Code | `.claude/agents/trellis-*.md` |
+| Cursor | `.cursor/agents/trellis-*.md` |
+| OpenCode | `.opencode/agents/trellis-*.md` |
+| Codex | `.codex/agents/trellis-*.toml` |
+| Kiro | `.kiro/agents/trellis-*.json` |
+| Gemini CLI | `.gemini/agents/trellis-*.md` |
+| Qoder | `.qoder/agents/trellis-*.md` |
+| CodeBuddy | `.codebuddy/agents/trellis-*.md` |
+| Factory Droid | `.factory/droids/trellis-*.md` |
+| Pi Agent | `.pi/agents/trellis-*.md` |
+
+Use the actual paths in the user project as authoritative.
+
+## Common Needs
+
+| Need | Which agent to edit |
+| --- | --- |
+| Research must write files, not only reply in chat | `trellis-research` |
+| Certain local specs must be read before implementation | `trellis-implement` + `implement.jsonl` configuration rules |
+| Specific commands must run during checking | `trellis-check` |
+| Agent must not modify certain directories | The corresponding agent's write boundary instructions |
+| Agent output format must be fixed | The corresponding agent's final/reporting instructions |
+
+## Modification Principles
+
+1. **Preserve role boundaries**: research investigates and persists; implement writes implementation; check reviews and fixes.
+2. **Do not hard-code project specs into agents**: long-term specs belong in `.trellis/spec/`; agents are responsible for reading them.
+3. **Make read order explicit**: active task -> PRD -> info -> JSONL -> spec/research.
+4. **Make write boundaries explicit**: which directories may be written and which may not.
+5. **Synchronize across platforms**: when the user configured multiple platforms, decide whether to change only the current platform or all platform agents.
+
+## Agent Pull Platforms
+
+If an agent file contains a prelude for "read task/context after startup," do not remove those steps when editing. Otherwise the agent will work only from chat context and bypass Trellis's core mechanism.
+
+## Hook Push Platforms
+
+If context is injected by a hook, the agent file should still retain responsibility boundaries. Do not remove PRD/spec requirements from the agent just because a hook injects context.