Bring the envs README up to date and register all 22 environments

[yichao-liang]

Summary

Brings predicators/envs/README.md up to date, with every claim re-measured on October 1, 2026.

Previews.
Each preview is now the solve GIF the RoboDisco site shows, linked to that environment's page, so the README and the site show the same demos.

All 22 environments.
The Gymnasium registry gains the seven RoboDisco environments it lacked (Balloons, Bridge, BusyBoard, Crane, IceRink, Launcher, Magnets).
All 22 build, reset, step and render through the wrapper with the Quick Start configuration.
The table lists all 22 with the site's descriptions and marks the five benchmark domains.

Columns, measured.

• Tasks: whether initial states vary across three train and three test tasks. Ants, Circuit and Float were wrongly marked fixed.
• Skills: whether get_gt_options builds a skill library.
• Oracle (was Demos): which approach solves the test task with the README command in the default configuration.
  The old column claimed Boil, Domino, Fan, Float and Grow; today the default configuration solves Ants, Balance, Blocks, Circuit, Cover, Crane, Launcher and Magnets with oracle, and Grow with oracle_process_planning.
  Boil and Bridge solve with oracle_process_planning under the settings of their oracle tests.
  The notes say why the rest fail.
  The pre-refactor commit 72d7258ed gives the same results, so the refactor did not cause any of them.

Fixes to stale or broken text.

• The note that Circuit, Cover, Laser and Switch fail to build was wrong: every environment builds alone. Circuit, Laser and Switch fail only when another environment was built earlier in the same process, and the README now says so.
• The Standalone API example passed a raw array to env.step, which raises; it now wraps it in Action.
• New: task selection and seeding through reset(), the observation layout, the benchmark settings file, and the two skill libraries (CFG.skill_library).

The smoke script and the notebook count 22 environments, and the smoke script no longer blames missing CFG for the same-process failures.
The environment bugs found along the way (the same-process failures, and the default-configuration crashes in Domino, Fan, Grow and Coffee) are left for a separate change.

Test plan

• Every README Python snippet runs (Quick Start, configuration, make overrides, Standalone API).
• tests/envs/test_robodisco.py passes with 22 environments.
• scripts/robodisco_getting_started.py builds all 22 environments in one process; only Circuit, Laser and Switch fail, as documented.
• Oracle column: the README command with both oracle approaches on every environment, on this branch and at 72d7258ed.
• GitHub's rendered README serves all 22 previews through its image proxy.

🤖 Generated with Claude Code