[Docs] Docs for ABI Stability

[tarang-jain]

Closes #1683

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: 88325713-383b-4992-a151-b584561af2b4

📥 Commits

Reviewing files that changed from the base of the PR and between 7cf69cb and 54a68ea.

📒 Files selected for processing (2)

• docs/source/abi_stability.rst
• docs/source/index.rst

---

📝 Walkthrough

Summary by CodeRabbit

• Documentation
  • Added comprehensive ABI stability guide covering compatibility criteria, safe and unsafe changes, handling of incompatible changes, and developer best practices.

Walkthrough

The PR adds comprehensive ABI stability documentation to cuVS, covering compatibility rules, naming conventions, struct handling, and developer guidance. Documentation is then integrated into the main index.

Changes

ABI Stability Documentation

Layer / File(s)	Summary
Core Documentation Content docs/source/abi_stability.rst	New file containing 441 lines covering ABI stability guarantees, safe/unsafe changes, struct stability, handling incompatible changes, consolidation strategies, and developer checklists.
Documentation Integration docs/source/index.rst	abi_stability.rst added to the Contents toctree for navigation.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~15 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Description check	❓ Inconclusive	No description was provided by the author, making it impossible to verify if it relates to the changeset.	Add a brief description explaining the purpose and scope of the ABI stability documentation being added.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: adding documentation for ABI stability concepts and guidelines.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[cjnolet]

@tarang-jain, apologies for wasting your time here. Since I am having to redo all the docs to convert them from Sphinx to Fern, I went ahead and added this file into the new docs (and I also generated a simpler version for end-users in addition to this version, which is intended for the developer guide). This PR can be closed.