Incorrect NCIT identifier for Radical Cystoprostatectomy in urothelial carcinoma example

The following text is from my agent, but I checked it for correctness and relevance. The agent found this when running linkml-validate over the examples

///

## Problem

The urothelial carcinoma example assigns `NCIT:C5189` the label `Radical Cystoprostatectomy`. Current NCIT resolves these identifiers as:

- `NCIT:C5189` — Breast Extraskeletal Osteosarcoma
- `NCIT:C51899` — Radical Cystoprostatectomy
- `NCIT:C94464` — Prostatocystectomy

This was detected by ontology term/label validation:

```text
Label mismatch for NCIT:C5189: expected Breast Extraskeletal Osteosarcoma, got Radical Cystoprostatectomy
```

## Affected locations

- `src/test/java/org/phenopackets/schema/v1/examples/UrothelialCarcinomaExample.java`
- `src/test/java/org/phenopackets/schema/v2/examples/UrothelialCarcinomaExample.java`
- `docs/cancer-example-java.rst`
- `docs/cancer-example.rst`

The prose in `docs/cancer-example.rst` already links Radical Cystoprostatectomy to `NCIT:C51899`, but the example block uses `NCIT:C5189`. The Java examples are also internally inconsistent: their comment names Prostatocystectomy (`NCIT:C94464`), while the constructed ontology class uses `NCIT:C5189` with the Radical Cystoprostatectomy label.

## Suggested correction

If the intended concept is Radical Cystoprostatectomy, replace `NCIT:C5189` with `NCIT:C51899` and reconcile the Java comment. It may also be useful to add identifier/label validation for ontology-backed example terms so unrelated but syntactically valid identifiers are caught automatically.

Start with the four affected files: the v1 and v2 UrothelialCarcinomaExample.java files and the two cancer example RST documents. Compare the existing NCIT identifiers, labels, comments, and links, then run linkml-validate over the examples. Done means the intended Radical Cystoprostatectomy identifier is consistent and the label validation no longer reports this mismatch.

Written by the indexing model from the issue text.