docs(blog): deep dive into the OmegaConf inventory backend

[Moep90]

Draft until #1537 and #1538 (the SEO frontmatter gate) merge — this post depends on the title/description frontmatter those PRs enforce.

What

A new blog post, docs/pages/blog/posts/omegaconf-backend-deep-dive.md, walking through the OmegaConf inventory backend: what it gives us over reclass, how interpolation and deferred evaluation work, and the literal ${escape:...} syntax from #1445.

Why

The OmegaConf backend has grown some genuinely useful features that are easy to miss if you only know reclass — dot-notation interpolation, oc.select/oc.env defaults, conditional resolvers, deferred \${...} evaluation, and custom Python resolvers. The literal-vs-deferred escape distinction in particular trips people up constantly, and #1445 plus the doc clarifications in #1521 finally made it unambiguous. I wanted one practical, opinionated post that ties it together so people know when reaching for the backend is worth it.

Approach

First person, practical, in the established blog voice. Every flag, YAML snippet, and behaviour claim is grounded in the existing docs and source — I deliberately did not invent anything:

• Install/enable/dotfile config and the --migrate migration table from docs/pages/inventory/omegaconf.md.
• .yaml class support framed against fix(omegaconf): resolve --migrate flag and .yaml class support #1483.
• The ${escape:...} literal behaviour, including the key-collision case and the __KAPITAN_LITERAL__ marker mechanism, taken straight from kapitan/inventory/backends/omegaconf/resolvers.py and the feat: add literal resolver to emit backslash dollar syntax in OmegaConf #1445 description.
• Examples mirror the real test inventory in tests/test_resources/omegaconf/inventory/classes/components/test-resolvers.yml.
• A !!! note admonition spells out the \${...} (deferred) vs ${escape:...} (literal) difference, since that is the single most common point of confusion.

Verification

• Confirmed the YAML frontmatter parses and that title (46) and description (131) land inside the SEO gate ranges.
• Cross-checked the escape behaviour and marker constants against the backend source rather than guessing.
• Did not run pytest or build the docs site, per the scope of this change.