migrate-turbo-files

# Migrate Turbo Files Current layouts: - Unexpanded shells live in `.turbo/shells/` with `spec:` and `depends_on:` frontmatter. - Plans live in `.turbo/plans/` with `status:` (required) and optional `spec:` for provenance. - `.turbo/improvements.md` entries use Type values `direct`, `investigate`, or `plan`. Legacy values `trivial` and `standard` map to `direct` and `plan` respectively. This skill migrates legacy shapes to those layouts. ## Task Tracking Use `TaskCreate` to create a task for each step: 1. Scan and classify existing files 2. Migrate prompt plan indexes 3. Process remaining files in `.turbo/plans/` 4. Normalize frontmatter on remaining plans 5. Migrate `improvements.md` Type values 6. Clean up and report ## Step 1: Scan and Classify Existing Files Scan for all legacy shapes: - **Prompt plan indexes** — Glob `.turbo/prompt-plans/*.md`. Also check for `.turbo/prompts.md` (oldest legacy format). Parse each index to determine whether prompts are inline (contain `### Prompt` sections with code blocks) or reference separate shell files (contain `**Shell:**` fields). Record the set of shell files each index references — Step 3 will skip these. - **Files in `.turbo/plans/*.md`** — Read each file's first 20 lines and classify: - **Unexpanded shell** — has legacy `type: shell` frontmatter AND does not contain `## Pattern Survey`, OR has no frontmatter but contains `## Produces`, `## Consumes`, and `## Covers Spec Requirements` without `## Pattern Survey`. Targ...