Migrate docs site from custom Antora to docouture (versioned, git-flow)

## Context

The current `docs/` Antora site is hand-built: custom `ui-bundle.zip` + `supplemental-ui/`,
manual Kroki Docker wiring in every CI workflow, `@antora/lunr-extension` for search,
`.docsconfig.yml`-driven release bumping. We're migrating it onto
[docouture](https://inditextech.github.io/docouture/prerelease/) (`0.1.0-SNAPSHOT.74.1`),
which replaces that machinery wholesale while keeping the ~140 existing `.adoc` pages.

Six docouture agent skills are already installed at repo root (`skills-lock.json`) — no
site migration has started, only the skill definitions.

## Decisions made

- **Scaffold**: `docouture new karatetools-oss --mode versioned --flow git-flow
--integration-branch develop --release-branch main --title "InditexTech Karate Tools"`
- **Structure**: `ROOT` (home only) + `main` (everything) — **no promoted Guides module**.
Guides lives as a subfolder tree under `main/pages/guides/`, nested per topic
(`guides/archetype/`, `guides/configuration/`, `guides/open-api-generator/`,
`guides/clients/`, `guides/execution/`), one `main` `nav.adoc`.
- **Existing `docs/vX.Y.Z` tags**: already tag-compatible with docouture's Versioned mode
(`docs/v*` matcher, same component name at every historical tag) — **left untouched**.
Each old tag keeps building from its own snapshot (old `HOME`-module nav) forever;
only forward builds get the new structure.
- **This migration ships as a republish of `docs/v6.0.0` in place**, not a version bump.
`docs/.docsconfig.yml`'s staged `6.1.0` is unrelated (no real product release behind
it) and is left alone. Cut via manual `workflow_dispatch` of `docouture-release.yml`
with version input `6.0.0` — force-recreates that tag at `main`'s new tip, per
docouture's documented republish mechanic. `docs/.release-version` is **not** advanced
(republish path skips the forward bump).
- **Old→new URL redirects required** as part of this same migration (not a follow-up) —
republishing `6.0.0` in place changes page paths (`HOME:index.adoc` → `ROOT:index.adoc`,
`configuration:karate-config.adoc` → `main:guides/configuration/karate-config.adoc`,
etc.), so anything bookmarking/indexing the current `6.0.0` site 404s without a mapped
`redirects:` block on the antora-extensions registration.
- **Favicon**: current `favicon.ico`/`favicon.png` (32×32, full-colour gear+sunburst+
gradient+figure) fails docouture's flat/single-colour favicon guidance at that size —
needs a new simplified derivative (figure silhouette alone, one solid colour).
- **Product logo**: `logo.png` (180×180, square, no wordmark) is directly reusable for
`product_logo` as-is. `product_logo_dark` needs a readability check against the actual
dark theme background before deciding if a separate dark variant is needed.

## Section → content mapping

| Section | Source |
|---|---|
| Overview (`about`, `architecture`, `glossary`) | README.md + archetype/module diagrams |
| Getting started (`prerequisites`, `quickstart`) | existing `prerequisites/*` + new quickstart (none exists today) |
| Guides (`overview` + per-topic) | archetype, configuration, open-api-generator, clients, execution — ~90 pages |
| Reference (`overview`, `configuration`, thin CLI/integrations) | mostly new — current site has almost no pure lookup-table content |
| Additional information (`overview`, `changelog`, `release-notes`, `eol`) | `release/*` existing; `changelog` needs authoring `code/CHANGELOG.md` (doesn't exist) |
| Contributing (`overview`, `development`) | `contributing/*`, replacing the 8-level anchor-xref hack in `karatetools-oss.adoc` with real subpages |
| Home (`ROOT/index.adoc`) | full rewrite — current page is a bare emoji-icon link grid, no prose/hero/FAQ; needs hero, intro pitch, Get started cards, Key capabilities (`[feature-tabs]`), OSS CTA, pre-adoption FAQ |

## Build machinery swapped out

- [ ] Custom `ui-bundle.zip` + `supplemental-ui/` → docouture's own themed UI bundle
(keep image-zoom-in if still wanted; Gherkin syntax highlighting via
jquery+highlight.js needs a Shiki-lang-support check before dropping)
- [ ] Manual Kroki Docker wiring in every workflow → docouture's built-in Kroki
(self-starting, `docouture eject/teardown kroki`) — 14 `.puml` partials should
port with minimal change
- [ ] `@antora/lunr-extension` → docouture's bundled search extension
- [ ] `docs-build_snapshot.yml` / `docs-publish.yml` / `docs-release.yml` / `docs-verify.yml`
→ docouture-generated `docouture-*.yml` workflow set
- [ ] `.docsconfig.yml` release-version bumping → `docs/.release-version`
- [ ] AGENTS.md scaffolded at repo root (doesn't exist yet)

## Non-goals

- No version bump — this is a docs re-styling/tooling migration only.
- No changes to any existing `docs/v4.0.0`…`docs/v6.0.0` tag other than `6.0.0` itself
(republished in place, per above).

Start by reading skills-lock.json, the existing docs/ tree, and docs-build_snapshot.yml, docs-publish.yml, docs-release.yml, and docs-verify.yml. Use the documented docouture scaffold and section mappings as the migration checklist; done means the forward site builds with the new structure, workflows and redirects are in place, and the 6.0.0 republish path is ready without changing older tags.

Written by the indexing model from the issue text.