docs: link Code Wiki for Apache Polaris as a navigation aid

[flyingImer]

New contributors (human and AI) spend real time building a mental map of Polaris's modules before they can make a focused change. The Code Wiki for Apache Polaris is a third-party, auto-generated overview of modules and their relationships that can shorten that ramp-up. This PR links it from README.md only.

Scope narrowed in response to review feedback. The initial version of this PR also added the link to CONTRIBUTING.md (as a new "Get oriented in the codebase" subsection) and AGENTS.md (as a pointer back to that subsection). Per @snazy's concern that the project should not appear to endorse content it cannot review or version, and @dimas-b's suggestion that the Code Wiki is better shared from a personal point of view, the Code Wiki reference is now only in README.md — outside contributor workflow docs — and framed explicitly as a third-party navigation aid, not authoritative.

Scope: docs only. No site/ content, no extension to dependencies.

Follow-up to #4276. Motivated by apache/polaris#1028 (comment).

Per @dimas-b's suggestion, I plan to mention this on dev@polaris.apache.org for visibility and broader input on the project's posture toward AI-generated external references.

Checklist

• 🛡️ Don't disclose security issues! (contact security@apache.org)
• 🔗 Clearly explained why the changes are needed, or linked related issues: follow-up to docs: add AGENTS.md coding guidelines for AI agents #4276
• 🧪 Added/updated tests with good coverage, or manually tested (and explained how): N/A (documentation only)
• 💡 Added comments for complex logic: N/A
• 🧾 Updated CHANGELOG.md (if needed): not needed for docs-only
• 📚 Updated documentation in site/content/in-dev/unreleased (if needed): not needed

[flyingImer]

@flyrain @dimas-b @adutra WDYT?

[dimas-b]

TBH, this CodeWiki is a lot of text... I glanced over it, but it's mostly TL;DR from my side 😅

Still, if people find it useful, why not link?

The preamble here looks correct to me.

[flyrain]

I'm OK if this wiki is reliable, up to date and accurate. It should be fine if the wiki is lacking behind from the code base a few days or so. Do we know how often the wiki get updated?

[dimas-b]

Let's mention this on dev maybe?... just for visibility.

[snazy]

Personally, I think that the referred content can be useful.

That wiki is, if I understand correctly, 100% AI generated. AIs make mistakes (citing Google's Gemini here ;) ), they can't be perfect ("... , so double check it.").

Is it better or worse than, for example, a blog post published elsewhere about Polaris? Probably not.

What concerns me is that we, as a project, do not and cannot control the content. If we point to it, we should be able to fully trust it.

If better orientation is needed, we can certainly have more README files around in the code base, which might be generated but would be reviewed and stay with the code base.
That would, assuming the READMEs stay up-to-date, solve the versioning issue, when that wiki refers to a totally different state of the code.

WDYT?

[dimas-b]

If trusting the wiki contents is a concern, perhaps making a blog post about it might be an alternative (rather than a direct link from CONTRIBUTING.md).

This way, ideas about Code Wiki are still shared, but from a personal point of view.

[flyingImer]

Thanks all for the feedback. Narrowed the scope in 0617c9d:

• Reverted the CONTRIBUTING.md subsection and the AGENTS.md pointer.
• Kept only the README.md paragraph, framed explicitly as a third-party navigation aid.

Rationale: @snazy's concern is structural. The project shouldn't appear to endorse content it cannot review or version. Keeping the link in README.md (where external-resource pointers are conventional) and out of contributor workflow docs (CONTRIBUTING.md, AGENTS.md) should address that, without losing the orientation benefit for newcomers. The "not authoritative, verify against source" caveat stays in the text.

On @flyrain's question about update frequency: I don't have a public SLA from codewiki.google. If that's a blocker, happy to drop the link entirely and pivot to @dimas-b's blog-post suggestion.

Per @dimas-b's suggestion, I'll mention this on dev@polaris.apache.org for broader visibility and input on how the project wants to handle AI-generated external references going forward.