docs(platform): add resource tree and version table

[patrick-hermann-sva]

The README explained the shared contract well but never answered the first question a reader actually has: what does applying a Platform create, and which versions does it pull? Both were only discoverable by reading the Composition, then the wrapped flux-init module, then an EnvironmentConfig.

What's added

## What gets created — a mermaid tree plus a table of every composed resource: real name pattern, which Configuration emits it, and the condition. It makes the two-level structure explicit — platform composes child XRs, and the managed resources appear one level deeper, from flux-init's own Composition. Includes the crossplane beta trace output from the live kind1 run.

## Versions — every package pin (dependsOn, Crossplane floor), the xplane-flux-init OCI module, the fact that platform's own KCL is inline (nothing to publish), and the only two versions an XR normally sets: flux-operator chart 0.55.0 and Flux distribution 2.x, both from the flux-defaults EnvironmentConfig.

Accuracy

• Name patterns ({}-flux-operator, {}-flux-instance, {}-flux-instance-uses-operator, {}-observe-rc, {}-source-{}, {}-sops-age) are read out of xplane-flux-init/main.k, and {}-flux-init out of platform's Composition — not invented.
• Version rows cross-checked against crossplane.yaml and flux-init/examples/environment-config.yaml.
• The trace block is real output from the kind1 test, not mocked.
• Fixed a miscount while writing: a minimal Platform composes four objects, not five.

On the diagram

mermaid-cli can't run in this environment (it needs chromium), so I could not render-validate it — only check it structurally (every referenced node declared, every node reachable and classed). Because of that I deliberately kept the syntax to <br/> and plain labels instead of <b>/<code>, which are less certain to render on GitHub. Worth a quick look at the rendered preview before merging.

🤖 Generated with Claude Code

[github-actions]

📦 ttl.sh preview packages

Preview OCI packages for the Configurations changed in this PR, pushed to the public, ephemeral ttl.sh registry. No auth required — install on any Crossplane v2 cluster:

📦 bootstrap/platform → ttl.sh/stuttgart-things/crossplane-configurations-pr102-f760487/platform:24h

apiVersion: pkg.crossplane.io/v1
kind: Configuration
metadata:
  name: platform-preview
spec:
  package: ttl.sh/stuttgart-things/crossplane-configurations-pr102-f760487/platform:24h

Note

Images expire 24h after the last push (ttl.sh's maximum TTL); push a new commit to refresh them. The Configuration name is suffixed -preview so it won't clash with a canonical install.