Add doc pages for notable Atari environment sets

[BolunDai0216]

Description

Fixes #708

Adds sidebar-visible documentation pages listing the games in each commonly benchmarked subset of Atari environments, so multiple views exist simultaneously as suggested in the issue:

• Atari 57 (environments/atari_57) — the 57 games of the DeepMind benchmark (DQN through Agent57), with references and a note that Defender/Surround were unavailable in atari-py, which is why some papers benchmark on only 55 of these games.
• Previously in OpenAI Gym (environments/gym) — the 62 games that were registered in OpenAI Gym, explaining the Pong-v0 → ALE/Pong-v5 naming migration and how the set relates to Atari 57 (all of it except Surround, plus Adventure, AirRaid, Carnival, ElevatorAction, JourneyEscape and Pooyan).
• Complete list — now included in a toctree (it previously wasn't in any), with cross-links to the set pages.

The Environments page gets a visible "Environment sets" section linking the three views, and the three pages live under a separate "Environment Sets" sidebar dropdown directly below Environments (per review, keeping the Environments dropdown to just the individual game pages).

The new pages follow the existing complete_list pattern: a checked-in env-grid HTML file embedded in a markdown page via {raw} html, using the same relative-link style (correct for the dirhtml builder used in CI). The grids were generated programmatically from the display names in complete_list.html, with assertions validating both set definitions and the relationship between them. Additional sets (e.g., the DQN Nature 49) can be added the same way if desired.

Sphinx build succeeds with no new warnings.

🤖 Generated with Claude Code

[pseudo-rnd-thoughts]

Thanks @BolunDai0216 for the PR. Reviewing this locally, I don't like "Complete List", "Atari 57" and "Environments Previously in Gym" being in the table of contents

Could you remove these from the table of contents and rename "Environments Previously in Gym" to "Previously in OpenAI Gym"

[jkterry1]

@pseudo-rnd-thoughts where are you asking for links to the pages to be places if not in the left hand bar? Perhaps they should go under a different "environment sets" drop down and not in the main environments drop down?

[pseudo-rnd-thoughts]

Currently the links exist in the environments root page and I don't think these need to exist anywhere in the table of contents. If we need to have them in the TOC, then as a single item below environments could work as well. I think we need to render these locally to see what looks good and is helpful

[jkterry1]

They do need to be in the TOC, Bolun can you please move them to a separate drop down item?

…

-------- Original Message --------

On Wednesday, 08/26/26 at 19:57 Mark Towers ***@***.***> wrote: pseudo-rnd-thoughts left a comment [(Farama-Foundation/Arcade-Learning-Environment#733)](#733 (comment)) Currently the links exist in the environments root page and I don't think these need to exist anywhere in the table of contents. If we need to have them in the TOC, then as a single item below environments could work as well. I think we need to render these locally to see what looks good and is helpful — Reply to this email directly, [view it on GitHub](#733?email_source=notifications&email_token=AEUF33HYOUPVSMON6NJI3Q35L52M7A5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTKNBTGI2DSOJUGE2KM4TFMFZW63VHMNXW23LFNZ2KKZLWMVXHJLDGN5XXIZLSL5RWY2LDNM#issuecomment-5432499414), or [unsubscribe](https://github.com/notifications/unsubscribe-auth/AEUF33DDMWVEOWGM3NI4HHD5L52M7AVCNFSNUABDKJSXA33TNF2G64TZHM2TQMJWGY2TIO2JONZXKZJ3GUZDEOJWHE2TENJXUF3AE). You are receiving this because you commented.Message ID: ***@***.***>

[BolunDai0216]

Done in 836d04b:

• The three set pages are removed from the Environments toctree. They now live under a separate "Environment Sets" dropdown directly below Environments in the sidebar (as @jkterry1 suggested), so the Environments dropdown again contains only the individual game pages.
• Renamed "Environments previously in Gym" → "Previously in OpenAI Gym" (page title and all cross-links).

The links on the Environments root page are kept as before. Rendered locally with the dirhtml builder — no new warnings, and the new dropdown is collapsed by default:

▸ Environments
▸ Environment Sets
    Complete List - Atari
    Atari 57
    Previously in OpenAI Gym
  ALE Vector Environment Guide
  ...

[jkterry1]

-Mark are you happy with this? -Can we put the sets of environments dropdown above environments just since that’s how normal menu hierarchy works for websites?

…

-------- Original Message --------

On Sunday, 08/30/26 at 19:50 Bolun Dai ***@***.***> wrote: BolunDai0216 left a comment [(Farama-Foundation/Arcade-Learning-Environment#733)](#733 (comment)) Done in [836d04b](836d04b): - The three set pages are removed from the Environments toctree. They now live under a separate "Environment Sets" dropdown directly below Environments in the sidebar (as ***@***.***(https://github.com/jkterry1) suggested), so the Environments dropdown again contains only the individual game pages. - Renamed "Environments previously in Gym" → "Previously in OpenAI Gym" (page title and all cross-links). The links on the Environments root page are kept as before. Rendered locally with the dirhtml builder — no new warnings, and the new dropdown is collapsed by default: ▸ Environments ▸ Environment Sets Complete List - Atari Atari 57 Previously in OpenAI Gym ALE Vector Environment Guide ... — Reply to this email directly, [view it on GitHub](#733?email_source=notifications&email_token=AEUF33BCXOWTEC2NEJ42UH35MS4STA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTKNBXGIYDENRZGAZ2M4TFMFZW63VHNVSW45DJN5XKKZLWMVXHJLDGN5XXIZLSL5RWY2LDNM#issuecomment-5472026903), or [unsubscribe](https://github.com/notifications/unsubscribe-auth/AEUF33BQIVBXAN4KGBCCY5D5MS4STAVCNFSNUABDKJSXA33TNF2G64TZHM2TQMJWGY2TIO2JONZXKZJ3GUZDEOJWHE2TENJXUF3AE). You are receiving this because you were mentioned.Message ID: ***@***.***>