Goal: add documentation to readme reflecting Claude and Codex's use of /goal

## Goal

Our readme should contain references to the use of `/goal` in Claude Code and Codex, with appropriate links. Not extended discussion, but we want to note that we are using this now-standard term.

We also want to make sure we link to https://github.com/githubnext/autoloop which also inspired this repo. Autoloop is a similar goal-driven agentic workflow, with more of an emphasis on scientific exploration.

## Completion Contract

The README.md "Built On" section (or a similar appropriate section) links to:
- Claude Code `/goal` documentation
- Codex `/goal` documentation
- https://github.com/githubnext/autoloop with a brief description

## Evidence / Verification

```bash
set -euo pipefail
grep -q "autoloop" README.md
grep -qi "claude" README.md
grep -qi "codex" README.md
grep -q "https://github.com/githubnext/autoloop" README.md
```

All commands must exit 0.

## Scope and Constraints

Allowed files:
- `README.md`

Do not remove existing content. Keep additions brief — a few lines, not paragraphs.

## Iteration Policy

This is a single-run goal. Read the current README, add the references, and verify.

## Blocked Stop Condition

If the official `/goal` documentation URLs for Claude Code or Codex cannot be found or confirmed, add placeholder references noting the feature and stop with a comment listing which URLs need human confirmation.

Start by reading README.md and locate the "Built On" section or another suitable place for brief references. Confirm the official Claude Code and Codex /goal documentation URLs, add both links plus a short description and link for githubnext/autoloop, then run the four grep commands in the issue to verify completion.

Written by the indexing model from the issue text.