Added the RitS TS search adapter

[alongd]

An adapter for executing RitS (Right into the Saddle) TS-guess jobs.

RitS is a flow-matching ML model that generates 3D transition-state geometries
directly from atom-mapped reactant + product structures, without requiring an
initial guess. Unlike GCN (which is restricted to isomerizations), RitS can
handle bimolecular reactions and supports charged species, so it covers a
strictly larger reaction space.

Code source : https://github.com/isayevlab/RitS
Paper : 10.26434/chemrxiv.15001681/v1
Pretrained ckpt : https://doi.org/10.5281/zenodo.19474153

[Copilot]

Pull request overview

This PR integrates a new TS-guessing pathway into ARC by adding a RitS (Right into the Saddle) adapter, along with installation tooling and CI support to manage RitS’s heavy ML dependency stack.

Changes:

• Added a new RitSAdapter TS job adapter plus a standalone runner script (rits_script.py) to execute RitS inference in an isolated rits_env.
• Added a dedicated RitS installer (devtools/install_rits.sh) and Makefile/install-all wiring (including a CI-safe --no-rits switch).
• Introduced a separate GitHub Actions lane to build/cache the RitS environment and smoke-test imports.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
Makefile	Adds install-rits target and excludes RitS from install-ci.
devtools/install_rits.sh	New installer to create rits_env, install torch/PyG stack, and download/verify checkpoint.
devtools/install_all.sh	Adds --no-rits flag and optional RitS installation.
arc/settings/settings.py	Registers RitS in defaults and adds helpers to locate the RitS repo + checkpoint.
arc/job/adapters/ts/rits_ts.py	Implements the RitS TS adapter and glue logic to convert outputs into TSGuess objects.
arc/job/adapters/ts/rits_test.py	Adds Tier-1 unit tests and gated Tier-2 end-to-end tests.
arc/job/adapters/ts/init.py	Ensures RitS adapter is imported/registered.
arc/job/adapters/scripts/rits_script.py	Standalone script invoked inside rits_env to run RitS and emit ARC-consumable YAML.
arc/job/adapter.py	Adds rits to JobEnum.
.github/workflows/ci.yml	Adds a dedicated rits-install job to build/cache rits_env and smoke-test imports.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.39%. Comparing base (61a711a) to head (19f664c).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #859      +/-   ##
==========================================
+ Coverage   60.10%   60.39%   +0.29%     
==========================================
  Files         102      103       +1     
  Lines       31041    31210     +169     
  Branches     8082     8108      +26     
==========================================
+ Hits        18657    18850     +193     
+ Misses      10071    10023      -48     
- Partials     2313     2337      +24     

Flag	Coverage Δ
functionaltests	60.39% <ø> (+0.29%)	⬆️
unittests	60.39% <ø> (+0.29%)	⬆️

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