DOC: refresh README install path and CITATION.cff version

[HarshRajSinghania]

Summary

Updates identity-facing repo files that had drifted from current install and release practice.

Assisted-by: Grok (Grok 4.6)

Motivation

Closes #900 (remaining acceptance criteria after #941 replaced copilot-instructions.md with AGENTS.md).

• README install guidance still led with Anaconda Distribution as a prerequisite.
• CITATION.cff had no software version / date-released, so citation tooling only saw the 2024 JOSS article date.

Implementation

• README Installation section is pip-first; conda-forge remains the conda path and Anaconda Distribution is no longer presented as a prerequisite.
• CITATION.cff now has top-level version: 0.11.4 and date-released: 2026-07-14 (current tagged release). The preferred-citation JOSS article block is unchanged.
• docs/source/contributing.rst documents bumping those two fields as part of the release checklist.

Testing

• Reviewed the three-file diff against DOC: Freshness pass on contributor- and identity-facing files #900 acceptance criteria.
• Confirmed __init__.py / CHANGELOG list 0.11.4 (14 July 2026) as the current release used for the citation fields.
• Did not run the full test suite; this change is documentation-only.

I do not have cffconvert available in this environment. Maintainers can verify with:

cffconvert --validate

[mmcky]

Thanks for the README and CITATION.cff refresh, and welcome to QuantEcon.py!

One quick request that we now make of every pull request. QuantEcon has just adopted a Code of AI Use, which welcomes AI-assisted contributions and asks each pull request to say whether AI tools were used. Our pull-request template doesn't show this yet, so we're asking by hand. Could you:

1. Add one line to the description above: Assisted-by: <tool> (<model>) if AI tools meaningfully contributed (for example Assisted-by: Claude Code (Claude Fable 5.1)), or Assisted-by: none if they didn't.
2. Reply here to confirm that you chose the task, read the result, and will answer review on it.

We're asking everyone, so this isn't a flag on your pull request. Thanks!

[HarshRajSinghania]

Thanks @mmcky — added Assisted-by: Grok (Grok 4.6) to the description.

I chose this task from #900, read the resulting README / CITATION.cff / contributing checklist changes, and will answer review on them.

[mmcky]

Thanks @HarshRajSinghania. I pushed one commit (7015864) that drops the CITATION.cff hunk: #973 added version: 0.12.0 and date-released: 2026-09-24 to main for the 0.12.0 release, so these two lines would have duplicated both keys. Your README and contributing.rst changes are unchanged, and the new contributing note matches what #973 did. I have approved the CI runs and will merge once they pass.

[coveralls]

coverage: 94.0% (+0.007%) from 93.993% — HarshRajSinghania:docs/issue-900-freshness into QuantEcon:main