Added the ability to escape Jinja variables in recipes to include them in prompts

[peterwilli]

Summary

Currently, it is impossible to escape variables in recipes. This makes it impossible to create recipes that create other recipes (recipeception anyone?)

Why is this important?

Well, I have this recipe (note: I escaped the triple backticks otherwise github messes up the formatting):

id: recipe-creator
version: 1.0.0
title: "Recipe Creator"
description: "Specialized subagent for creating new Goose recipes"
instructions: |
  You are a recipe creation assistant. Your job is to help users create new Goose recipes in the proper YAML format.

  **Important**: The prompt template uses simple parameter substitution only (e.g., `{{'{{param_key}}'}}`). 
  You **cannot** use Jinja2, conditionals, loops, or filters. Only straight parameter replacement works.

  **Important**: When defining parameters, all optional variables **must** have default values. This ensures the recipe works even when optional parameters are not provided.

  When creating a recipe, you should:
  1. Ask clarifying questions to understand the recipe's purpose
  2. Determine the appropriate name, id, and description
  3. Identify required vs optional parameters
  4. **Ensure all optional parameters have default values** - this is required!
  5. Write clear instructions for what the subagent should do
  6. Use parameters in the prompt template with `{{'{{parameter_key}}'}}` syntax

  Default extensions available:
  - `developer`: file editing, shell commands, code analysis
  - `todo`: task management
  - `subagent`: delegation to other agents
  - `apps`: create HTML/CSS/JS applications

  **Always output the example format** at the end of your response so the user sees exactly what the recipe looks like.

activities:
  - Create new recipe definitions
  - Define appropriate parameters
  - Write clear instructions and prompts
  - Suggest suitable extensions
  - Save recipe to specified location
extensions:
  - type: builtin
    name: developer
    display_name: Developer
    timeout: 300
    bundled: true
  - type: builtin
    name: text_editor
    display_name: Text Editor
    timeout: 300
    bundled: true
parameters:
  - key: output_path
    input_type: string
    requirement: required
    description: "Path to save the recipe file (project-level: ./recipes/, global: ~/.config/goose/recipes/)"
  - key: recipe_name
    input_type: string
    requirement: optional
    default: "my-recipe"
    description: "Name/ID for the new recipe"
  - key: purpose
    input_type: string
    requirement: optional
    default: "task automation"
    description: "What this recipe should accomplish"
  - key: extensions
    input_type: string
    requirement: optional
    description: "Comma-separated list of extensions needed (developer, todo, apps, etc.)"
    default: "developer"

prompt: |
  Create a new Goose recipe based on the following:

  Recipe Name: {{recipe_name}}
  Purpose: {{purpose}}
  Required Extensions: {{extensions}}
  Output Path: {{output_path}}

  Use this exact format (keep all keys, adapt values as needed):

  ``yaml
  id: {{recipe_name}}
  version: 1.0.0
  title: "Human-Readable Title"
  description: "Clear description of what this recipe does"
  instructions: |
    You are a specialized subagent for [purpose].

    Your responsibilities include:
    - [Task 1]
    - [Task 2]
    - [Task 3]

    Guidelines:
    - [Guideline 1]
    - [Guideline 2]

  activities:
    - [Activity 1]
    - [Activity 2]
  extensions:
    - type: builtin
      name: developer
      display_name: Developer
      timeout: 300
      bundled: true
  parameters:
    - key: param_name
      input_type: string
      requirement: optional
      description: "Parameter description"
  prompt: |
    [Your prompt template here using {{'{{param_name}}'}} for parameter substitution]
  ``

  Save the recipe to: {{output_path}}

  **After saving the recipe, validate it by running:**
  ``
  goose recipe validate {{output_path}}
  ``
  If validation fails, fix any errors and save again until validation passes.

Without this PR, it is impossible to use this. So this opens the door to much much more use-cases for recipes! I made sure it follows original escaping behaviour of Jinja, see: https://tedboy.github.io/jinja2/templ7.html

Type of Change

• Feature
• Bug fix
• Refactor / Code quality
• Performance improvement
• Documentation
• Tests
• Security fix
• Build / Release
• Other (specify below)

AI Assistance

• This PR was created or reviewed with AI assistance

Testing

Related Issues

Relates to #ISSUE_ID
Discussion: LINK (if any)

Screenshots/Demos (for UX changes)

(see example recipe)

[jh-block]

Thank you!