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

.trellis/workflow.md

@@ -442,3 +442,33 @@ Following this workflow ensures:
 - [OK] Transparent team collaboration
 
 **Core Philosophy**: Read before write, follow standards, record promptly, capture learnings
+
+[workflow-state:no_task]
+No active task. **A Direct answer** — pure Q&A / explanation / lookup / chat; no file writes + one-line answer + repo reads ≤ 2 files → AI judges, no override needed.
+**B Create a task** — any implementation / code change / build / refactor work. Entry sequence: (1) `python3 ./.trellis/scripts/task.py create "<title>"` to create the task (status=planning, breadcrumb switches to [workflow-state:planning] for brainstorm + jsonl phase guidance) → (2) load `trellis-brainstorm` skill to discuss requirements with the user and iterate on prd.md → (3) once prd is done and jsonl is curated, run `task.py start <task-dir>` to enter [workflow-state:in_progress] for the implementation skeleton. For research-heavy work, dispatch `trellis-research` sub-agents — main agent must NOT do 3+ inline WebFetch / WebSearch / `gh api` calls. **"It looks small" is NOT grounds for downgrading B to A or C**.
+**C Inline change** (per-turn only, escape hatch for B) — the user's CURRENT message MUST contain one of: "skip trellis" / "no task" / "just do it" / "don't create a task" / "跳过 trellis" / "别走流程" / "小修一下" / "直接改" / "先别建任务" → briefly acknowledge ("ok, skipping trellis flow this turn"), then inline. **Without seeing one of these phrases you must NOT inline on your own**; do not invent an override the user never said.
+[/workflow-state:no_task]
+
+[workflow-state:planning]
+Load the `trellis-brainstorm` skill and iterate on prd.md with the user.
+Phase 1.3 (required, once): before `task.py start`, you MUST curate `implement.jsonl` and `check.jsonl` — list the spec / research files sub-agents need so they get the right context injected. You may skip only if the jsonl already has agent-curated entries (the seed `_example` row alone doesn't count).
+Then run `task.py start <task-dir>` to flip status to in_progress.
+Research output **must** land in `{task_dir}/research/*.md`, written by `trellis-research` sub-agents. The main agent should not inline WebFetch / WebSearch — the PRD only links to research files.
+[/workflow-state:planning]
+
+[workflow-state:in_progress]
+**Flow**: trellis-implement → trellis-check → trellis-update-spec → commit (Phase 3.4) → `/trellis:finish-work`.
+**Default (no override)**: dispatch the `trellis-implement` / `trellis-check` sub-agents — the main agent does NOT edit code by default. Phase 3.4 commit (required, once): after trellis-update-spec, or whenever implementation is verifiably complete, the main agent **drives the commit** — state the commit plan in user-facing text, then run `git commit` — BEFORE suggesting `/trellis:finish-work`. `/finish-work` refuses to run on a dirty working tree (paths outside `.trellis/workspace/` and `.trellis/tasks/`).
+**Sub-agent dispatch protocol (class-2 platforms: codex / copilot / gemini / qoder)**: When you spawn `trellis-implement` / `trellis-check` / `trellis-research`, your dispatch prompt **MUST** start with one line: `Active task: <task path from \`task.py current\`>`. No exceptions. These platforms have no hook to inject task context into sub-agents, so the sub-agent depends on this line; without it the sub-agent cannot find the task and will block to ask the user.
+**Inline override** (per-turn only, escape hatch for sub-agent dispatch): the user's CURRENT message MUST explicitly contain one of: "do it inline" / "no sub-agent" / "你直接改" / "别派 sub-agent" / "main session 写就行" / "不用 sub-agent". **Without seeing one of these phrases you must NOT inline on your own**; do not invent an override the user never said.
+[/workflow-state:in_progress]
+
+[workflow-state:completed]
+Code committed via Phase 3.4; run `/trellis:finish-work` to wrap up (archive the task + record session).
+If you reach this state with uncommitted code, return to Phase 3.4 first — `/finish-work` refuses to run on a dirty working tree.
+`task.py archive` deletes any runtime session files that still point at the archived task.
+[/workflow-state:completed]
+
+[workflow-state:my-status]
+your per-turn prompt text
+[/workflow-state:my-status]