docs: salvage database and configuration docs navigation from #2948

[serrrfirat]

Salvage of #2948 onto current main.

Summary

Cherry-picked the documentation updates from #2948 onto current origin/main.

This promotes the Database and Configuration docs pages from drafts into the live docs navigation, marks the superseded draft pages, and updates related onboarding/quickstart links.

Maintainer follow-up commits were added after salvage to:

• clarify that the Configuration page is an operator-focused reference checked against current config sources
• expand the page with provider-registry variables from providers.json
• add advanced configuration variables resolved by the current src/config/ modules

Original PR

• Original PR: docs: add Database and Configuration pages to live navigation #2948
• Original PR author: @Kampouse
• Original head branch: docs/add-database-page
• Original commit(s):
  • bf95084
  • 3f2547e
  • 9057f65
  • bd5bbf6
  • ecb4d32
  • 3368a18
  • 760e4aa
• Authorship preserved: yes for the cherry-picked original commits. This salvage branch also includes maintainer-authored follow-up commits:
  • docs: clarify configuration reference scope
  • docs: expand configuration variable reference

Salvage review

• Relevance: still relevant because the docs navigation lacked live Database and Configuration pages.
• Supersession check: current main did not already include equivalent live docs pages.
• Source-of-truth check: compared configuration claims against src/config/, providers.json, and src/setup/README.md; expanded the reference so all variables extracted from current src/config/*.rs and providers.json are represented, excluding test-only variables and OBSERVABILITY_BACKEND which is runtime-observability plumbing rather than operator docs in this page.
• Risk track: Track A, docs-only.

Validation

• jq empty docs/docs.json -> passed
• Simple docs navigation target check for docs/docs.json page/path refs -> passed
• Simple local link target check for changed docs -> passed
• git diff --check origin/main...HEAD -> passed
• Config-doc coverage script comparing docs/capabilities/configuration.mdx against current src/config/*.rs and providers.json -> passed (missing=0, ignoring test-only variables and OBSERVABILITY_BACKEND)

Notes

• No source-code changes.
• Branch was rebased onto current origin/main before update.
• Recommended merge method: rebase merge, to preserve original authorship.

[gemini-code-assist]

Code Review

This pull request introduces comprehensive documentation for IronClaw's configuration and database backends. It adds two new detailed guides covering environment variables and the comparison between PostgreSQL and libSQL, while updating the documentation structure and marking older drafts as superseded. Onboarding and quickstart guides were also updated to reflect these database options. Feedback was provided regarding a minor inconsistency in the database connection string examples where the username should be standardized to 'ironclaw' for clarity.

[gemini-code-assist]

The username in this example DATABASE_URL is user, which is inconsistent with the user ironclaw that is created in the manual setup instructions on line 71 and used in other examples throughout this document (e.g., lines 86, 192, and 214). To avoid confusion for users following the guide, it would be best to consistently use ironclaw as the username.

   export DATABASE_URL="postgres://ironclaw:***@localhost/ironclaw"

[Kampouse]

Please 🙏 lets get better docs 🥹