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/SKILL.md

@@ -0,0 +1,73 @@
+---
+name: trellis-meta
+description: "Understand and customize the local Trellis architecture inside a user project. Use when modifying .trellis plus platform hooks, settings, agents, skills, commands, prompts, or workflows generated by trellis init."
+---
+
+# Trellis Meta
+
+This skill is for local Trellis users who have already run `trellis init` in a project. After reading it, an AI should understand the Trellis architecture, operating model, and customization entry points inside that user project, then modify the generated `.trellis/` and platform directory files according to the user's request.
+
+The default operating scope is local files in the user project:
+
+- `.trellis/`: workflow, config, tasks, spec, workspace, scripts, and runtime state.
+- Platform directories: `.claude/`, `.codex/`, `.cursor/`, `.opencode/`, `.kiro/`, `.gemini/`, `.qoder/`, `.codebuddy/`, `.github/`, `.factory/`, `.pi/`, `.kilocode/`, `.agent/`, `.windsurf/`, and similar directories.
+- Shared skill layer: `.agents/skills/`.
+
+Do not assume the user has the Trellis source repository. Do not default to modifying the global npm install directory or `node_modules`.
+
+## How To Use
+
+1. Read `references/local-architecture/overview.md` first to establish the local Trellis system model.
+2. If the request involves a specific AI tool, read `references/platform-files/platform-map.md` and the relevant platform file notes.
+3. If the user wants to change behavior, read `references/customize-local/overview.md`, then open the specific customization topic.
+4. Before editing, read the actual files in the user project and treat local content as authoritative.
+
+## References
+
+### Local Architecture
+
+- `references/local-architecture/overview.md`: The three-layer local Trellis architecture and customization principles.
+- `references/local-architecture/generated-files.md`: Files generated by `trellis init` and their customization boundaries.
+- `references/local-architecture/workflow.md`: Phases, routing, and workflow-state blocks in `.trellis/workflow.md`.
+- `references/local-architecture/task-system.md`: Task directories, active tasks, JSONL context, and task runtime.
+- `references/local-architecture/spec-system.md`: How `.trellis/spec/` is organized and injected.
+- `references/local-architecture/workspace-memory.md`: `.trellis/workspace/`, journals, and cross-session memory.
+- `references/local-architecture/context-injection.md`: Hooks, sub-agent preludes, and context injection paths.
+
+### Platform Files
+
+- `references/platform-files/overview.md`: How shared `.trellis/` files relate to platform directories.
+- `references/platform-files/platform-map.md`: Platform directories and paths for skills, agents, hooks, and extensions.
+- `references/platform-files/hooks-and-settings.md`: How settings/config files, hooks, plugins, and extensions connect to Trellis.
+- `references/platform-files/agents.md`: Local file responsibilities for `trellis-research`, `trellis-implement`, and `trellis-check`.
+- `references/platform-files/skills-and-commands.md`: Differences between skills, commands, prompts, and workflows, plus how to change them.
+
+### Local Customization
+
+- `references/customize-local/overview.md`: Choose the right local customization entry point for the user's request.
+- `references/customize-local/change-workflow.md`: Change phases, routing, next actions, and workflow-state.
+- `references/customize-local/change-task-lifecycle.md`: Change task creation, status, archive behavior, and hooks.
+- `references/customize-local/change-context-loading.md`: Change how tasks, specs, journals, and hook context are loaded.
+- `references/customize-local/change-hooks.md`: Change platform hooks, settings, and shell session bridges.
+- `references/customize-local/change-agents.md`: Change research, implement, and check agent behavior.
+- `references/customize-local/change-skills-or-commands.md`: Add or modify local skills, commands, prompts, and workflows.
+- `references/customize-local/change-spec-structure.md`: Adjust the project spec structure under `.trellis/spec/`.
+- `references/customize-local/add-project-local-conventions.md`: Put team rules into project-local specs or local skills.
+
+## Current Rules
+
+- `.trellis/workflow.md` is the local workflow source of truth.
+- `.trellis/config.yaml` is the project-level Trellis configuration and task hook configuration entry point.
+- `.trellis/spec/` stores the user's project-specific coding conventions and design constraints.
+- `.trellis/tasks/` stores task PRDs, technical notes, research files, and JSONL context.
+- `.trellis/workspace/` stores developer journals and cross-session memory.
+- Platform settings/config files decide which hooks, agents, skills, commands, prompts, and workflows actually run.
+- `.trellis/.template-hashes.json` and `.trellis/.runtime/` are management/runtime state files. Confirm necessity before editing them.
+
+## Do Not
+
+- Do not treat Trellis upstream source code as the default target for local customization.
+- Do not modify the global npm install directory or `node_modules/@mindfoldhq/trellis` to implement project needs.
+- Do not overwrite user-modified local files with default templates.
+- Do not put team-private project rules into the public `trellis-meta`; put project rules in `.trellis/spec/` or a project-local skill.
+- Do not describe removed historical mechanisms as current Trellis behavior.