New Exec Type

---
name: new-exec-type
description: Add a new executable type to the flow runner (a new kind of automation block users can define in .flow files).
disable-model-invocation: true
argument-hint: "<type-name> — description of what this executable type does"
allowed-tools: mcp__flow__execute, mcp__flow__run_command, mcp__flow__list_executables, Bash(flow generate:*), Bash(flow validate:*), Bash(flow build:*), Bash(go test:*), Read
---

Add a new executable type to the flow runner for: $ARGUMENTS

An "executable type" is a new automation block users can declare in `.flow` files (like `exec`, `serial`, `parallel`, `render`). Follow these steps in order:

1. **Schema first** — add the new type's fields to `types/executable/executable_schema.yaml`.
   Read the existing schema to match the structure. Regenerate with the `generate` executable
   (`mcp__flow__execute`, ref `generate`) — it rewrites `types/executable/executable.gen.go`.
   Never edit the `.gen.go` file directly.

2. **Runner handler** — each type is its own package: create `internal/runner/<type>/<type>.go`.
   Read `internal/runner/exec/exec.go` or `internal/runner/serial/serial.go` as reference for the
   exact interface and pattern.

3. **Register the type** — wire the new handler into `internal/runner/runner.go` (the dispatch table).

4. **Parser support** — update `internal/fileparser/` if needed to recognize and validate the new type during YAML parsing.

5. **Tests** — add unit tests in `internal/runner/<type>/<type>_test.go` using Ginkgo.
   Use `Describe`/`It`/`Entry` — never `FDescribe`/`FIt`. Cover happy path and error cases.

6. **Validate** — run the `validate` executable (`mcp__flow__execute`, ref `validate`) to confirm
   generate, lint, and tests all pass.

Do not skip the schema step — editing generated files directly will cause CI to fail.