CAMEL-21208: Expand TemplateHelper tests to cover all templates

Comprehensive test coverage for all 23 FreeMarker templates:
- FreeMarker-processed templates (processTemplate): code-java, main,
  spring-boot-main, Dockerfile21/25, readme, readme.native,
  rest-dsl.yaml, run-custom-camel-version, main-pom (with deps,
  repos, jib/jkube), spring-boot-pom, quarkus-pom
- Init templates (raw text loading): java, yaml, xml, kamelet
  source/sink/action, pipe, integration

Tests verify: license header stripping, placeholder resolution,
conditional rendering, list iteration, Maven ${} passthrough,
Kamelet {{}} passthrough, and missing template error handling.

Also regenerate jbang command docs after rebase.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: gnodet