docs(tutorials): rewrite index as table with Colab badge column

[sergiopaniego]

Summary

Rewrites docs/source/tutorials/index.md from a minimal bullet list into a table that describes what each tutorial covers and whether a GPU is required. The toctree isupdated to include all eight tutorials in the current + in-progress set.

Must be merged after all prerequisite PRs below. Until those land, the Sphinx build will warn about missing pages (end-to-end-walkthrough, sft-warmup, rubrics, mcp-environment, evaluation-inspect).

Prerequisites (merge in any order before this PR)

PR	Tutorial added
#601	wordle-grpo migrated to environment_factory
#599	rubrics — composable reward computation
#602	mcp-environment — MCP tools in training and eval
#618	end-to-end-walkthrough — full GRPO pipeline
#628	evaluation-inspect — evaluating with Inspect AI
#471	feature/harness-interface — required by #636
#636	sft-warmup — SFT warm-up for GRPO

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation
• New environment
• Refactoring

Alignment Checklist

Before submitting, verify:

• I have read .claude/docs/PRINCIPLES.md and this PR aligns with our principles
• I have checked .claude/docs/INVARIANTS.md and no invariants are violated
• I have run /pre-submit-pr (or bash .claude/hooks/lint.sh and tests) and addressed all issues

RFC Status

• Not required (bug fix, docs, minor refactoring)

Test Plan

• After all prerequisite PRs are merged, rebase this branch on main
• Run cd docs && make html — build should complete with zero warnings about missing tutorial pages
• Open _build/html/tutorials/index.html — confirm table renders correctly with all 8 rows linked

Claude Code Review

Automated Checks

• Lint: PASS (docs-only change)
• Debug code: CLEAN

Tier 1: Fixes Required

None.

Tier 2: Alignment Discussion

None. Pure docs rewrite with no API surface changes.

[greptile-apps]

Greptile Summary

This PR rewrites docs/source/tutorials/index.md from a short bullet list into a structured table that describes each tutorial's scope, GPU requirement, and provides Colab launch badges. The toctree is also expanded from 3 to 8 entries to cover the full tutorial set being added by prerequisite PRs.

• The table format is a clear improvement: GPU requirements and Colab links are now scannable at a glance.
• One Colab badge link (Wordle GRPO row) is broken — it links to a plain github.com/huggingface/trl/blob/... URL rather than the colab.research.google.com/github/... equivalent; users clicking that badge will land in GitHub's file viewer instead of Colab.
• Five toctree entries (end-to-end-walkthrough, sft-warmup, rubrics, mcp-environment, evaluation-inspect) reference pages not yet merged, which will produce Sphinx warnings until the listed prerequisite PRs land.

Confidence Score: 4/5

Safe to merge after fixing the broken Colab link; the rest of the change is straightforward documentation.

The Wordle GRPO 'Open In Colab' badge navigates to a raw GitHub blob URL instead of Colab, so every user who clicks it on the published docs will land in GitHub's file viewer instead of opening the notebook. The fix is a one-word prefix change to the URL. Everything else in the PR — table layout, GPU flags, descriptions, toctree ordering — looks correct.

docs/source/tutorials/index.md — specifically line 6, the Wordle GRPO Colab badge URL.

Important Files Changed

Filename	Overview
docs/source/tutorials/index.md	Rewrites tutorial listing from bullet list to a rich table with GPU indicator and Colab badge columns; toctree expanded to 8 entries. One Colab badge link is broken (points to a GitHub blob URL instead of a Colab URL).

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Tutorials Index Page] --> B[Table Row: OpenEnv Tutorial]
    A --> C[Table Row: Wordle GRPO]
    A --> D[Table Row: RL Training 2048]
    A --> E[Table Row: End-to-end Walkthrough]
    A --> F[Table Row: SFT Warm-up for GRPO]
    A --> G[Table Row: Rubrics]
    A --> H[Table Row: MCP Tools]
    A --> I[Table Row: Evaluating with Inspect AI]
    B --> B1["Colab: colab.research.google.com - OK"]
    C --> C1["Colab: github.com/huggingface/trl - WRONG HOST"]
    D --> D1["No notebook"]
    E --> E1["Colab: colab.research.google.com - OK"]
    F --> F1["Colab: colab.research.google.com - OK"]
    G --> G1["Colab: colab.research.google.com - OK"]
    H --> H1["Colab: colab.research.google.com - OK"]
    I --> I1["Colab: colab.research.google.com - OK"]

Loading

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
docs/source/tutorials/index.md:6
The "Open In Colab" badge for the Wordle GRPO row links to a plain GitHub blob URL (`github.com/huggingface/trl/blob/...`) instead of the `colab.research.google.com/github/...` form. Clicking the badge takes users to GitHub's file viewer rather than opening the notebook in Colab, which defeats the purpose of the badge entirely.

```suggestion
| [Wordle GRPO](wordle-grpo.md) | Train an agent to play Wordle using GRPO via TRL's `environment_factory`. Shows the multi-turn tool-calling loop: the model guesses a word each turn and receives letter-position feedback until it wins or the episode ends. | Yes | [![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/huggingface/trl/blob/main/examples/notebooks/openenv_wordle_grpo.ipynb) |
```

_{Reviews (1): Last reviewed commit: "docs(tutorials): add Colab badge for MCP..." | Re-trigger Greptile}

[burtenshaw]

Approved per maintainer merge request after required checks passed.

[burtenshaw]

Approved per maintainer merge request after conflict resolution and required checks passed.