Adds Codex Playground feature

[thegovind]

This pull request introduces a "Codex Playground" feature, allowing users to execute natural language coding tasks within a specified repository using GitHub Actions.

Key changes include:

• Creation of a new workflow (codex-playground.yml) to execute Codex tasks via GitHub Actions.
• Addition of API endpoints to trigger tasks and fetch their statuses/logs.
• A new frontend component (PlaygroundModal) to provide a user interface for specifying tasks and monitoring their execution.
• Instructions in .github/copilot-instructions.md to guide agent integration with GitHub actions.

[Copilot]

Pull Request Overview

This PR adds a Codex Playground feature to allow users to run natural language coding tasks via GitHub Actions. Key changes include:

• A new GitHub Actions workflow (codex-playground.yml) that dispatches tasks.
• New API endpoints and schemas in the backend for starting tasks and retrieving their statuses/logs.
• A new UI component (PlaygroundModal) in the frontend with integrated task polling and example prompts.

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
frontend/tsconfig.tsbuildinfo	Updated build info with a new entry for MultiDevinModal.
frontend/src/components/ui/PlaygroundModal.tsx	New modal component to collect and submit Codex tasks and display task status updates.
frontend/src/components/HomePage.tsx	Default agent category updated to 'all'.
frontend/src/components/AgentCard.tsx	Added a Playground button and integrated the PlaygroundModal component for the codex-cli agent.
frontend/src/App.css	Added styling for the PlaygroundModal and its associated elements.
backend/app/services/github.py	Added functions for creating runner tokens, dispatching workflows, and retrieving logs/runs.
backend/app/models/schemas.py	New schemas added to support Codex Playground requests and responses.
backend/app/main.py	New endpoints to start a playground task, check task status, and download logs.
.github/workflows/copilot-setup-steps.yml	Workflow for validating Copilot setup changes.
.github/workflows/codex-playground.yml	Workflow definition for Codex Playground tasks with a disabled job.
.github/copilot-instructions.md	Updated integration instructions for GitHub Actions and general coding guidelines.

Comments suppressed due to low confidence (3)

frontend/src/components/AgentCard.tsx:237

• The code splits the 'repoName' prop to derive the owner and repository values. Ensure that 'repoName' is always in the format 'owner/repo' or consider passing these values explicitly to avoid potential mismatches.

          repoOwner={repoName?.split('/')[0] || ''}

.github/workflows/codex-playground.yml:20

• The default value for 'azure_openai_deployment' in the workflow ('o4-mini') is inconsistent with the defaults used in the frontend and backend ('gpt-4o'). Consider unifying these defaults.

        default: "o4-mini"

backend/app/main.py:393

• Relying on substring matching of 'task_id' in the html_url to identify workflow runs may be unreliable; consider including the task_id explicitly in the workflow inputs or another stable identifier for mapping.

            if task_id in str(run.get("html_url", "")):