docs: lead Quickstart with the indices file (fix stale PyPI description)

[CryptoFewka]

The README Quickstart renders as the PyPI project description, and it still framed the fastest path as a local beacon node (localhost:5052) + a /etc/optimum pubkeys file, implying keysync runs on the validator host.

Lead instead with KEYSYNC_INDICES_FILE (a JSON records file, no beacon needed) pointing at examples/indices.json, and present the BLS-pubkeys + beacon path as an alternative with a generic host. This matches the dashboard API-key boilerplate (#222).

Docs only. Note: PyPI descriptions are immutable per version, so this reaches pypi.org only via a new release (suggest cutting 1.1.1 after merge).

Written with Claude Code

Summary by CodeRabbit

• Documentation
  • Updated the quickstart instructions to better describe the simplest way to get started with a JSON file of records.
  • Clarified how validator tracking works, including support for using either a BLS pubkey or a bare index.
  • Added guidance that a beacon node can fill in the remaining validator details when needed.

[coderabbitai]

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository: getoptimum/coderabbit/.coderabbit.yaml

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Plan: Pro

Run ID: 8c75c4f1-90fa-468e-a865-ce25e583dd9a

📥 Commits

Reviewing files that changed from the base of the PR and between 176bf3d and 58a9f1c.

⛔ Files ignored due to path filters (1)

• LICENSE is excluded by none and included by none

📒 Files selected for processing (1)

• src/optimum_keysync/__init__.py

📝 Walkthrough

Walkthrough

The README Quickstart was updated. It now describes starting keysync from a JSON records file, mentions the indices file environment variable, and adds guidance for tracking validators by BLS pubkey or bare index, including a beacon-node-based example.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Possibly related PRs

• getoptimum/optimum-gateway#768: Both PRs update README quickstart and connection wording for Optimum tooling.
• getoptimum/optimum-keysync#8: Both PRs adjust keysync README guidance for validator input formats and beacon-node resolution.

🚥 Pre-merge checks | ✅ 5 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Title check	⚠️ Warning	The title is relevant, but it exceeds 72 chars and does not follow the required docs(<domain/pkg>): format.	Use docs(readme): lead Quickstart with the indices file.

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Description check	✅ Passed	The PR objectives clearly match the README-only Quickstart rewrite and PyPI-description note.
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.

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