Fix changelog bundle --no-resolve

[lcawl]

Summary

While testing #2773 I discovered that the bundle.resolve in the changelog configuration file was overruling the docs-builder changelog bundle command option --no-resolve.
This PR fixes that behaviour so that the command options have precedence over the config options.

Steps to test

I tested this PR against files in elastic/kibana#250840

1. Verify that the changelog configuration file has bundle.resolve setting. For example:

   bundle:
   # Whether to resolve (copy contents) by default
   resolve: true

2. Create a bundle with the --no-resolve option. For example:

   docs-builder changelog bundle \                                                                                                  
   --config ~/Documents/GitHub/kibana/docs/changelog.yml \
   --input-products "kibana 9.3.0 *" \
   --directory ~/Documents/GitHub/kibana/docs/changelog \
   --output ~/Documents/GitHub/kibana/docs/releases/kibana/9.10.0.yaml \
   --repo kibana --owner elastic \
   --output-products "kibana 9.10.0 *" \
   --no-resolve

Before this PR, the command-line option was ignored and the bundle was created with resolved details, for example:

products:
- product: kibana
  target: 9.10.0
  repo: kibana
entries:
- file:
    name: 238646.yaml
    checksum: 43bf0846eeb1363b4c697cbdaf2438344d327b56
  type: feature
  title: Edit feature condition and add feature discover url
  products:
  - product: kibana
    target: 9.3.0
  areas:
  - Management
  pr: "238646"
  issues:
  - https://github.com/elastic/kibana/issues/238178

With this PR fix, the command line option is heeded. For example:

products:
- product: kibana
  target: 9.10.0
  repo: kibana
hide-features:
- test_feature1
entries:
- file:
    name: 238646.yaml
    checksum: 43bf0846eeb1363b4c697cbdaf2438344d327b56
- file:
    name: 244072.yaml
    checksum: 186d612d19a18c671913dc0d1dabe558f5e1f3ad

Implemention details

src/services/Elastic.Changelog/Bundling/ChangelogBundlingService.cs

• BundleChangelogsArguments.Resolve: bool → bool? so null (unspecified), true (--resolve), and false (--no-resolve) are all distinguishable.
• ApplyConfigDefaults: input.Resolve || config.Bundle.Resolve → input.Resolve ?? config.Bundle.Resolve — uses ?? so an explicit false from the CLI is never overridden by the config.
• BuildBundle call site: input.Resolve → input.Resolve ?? false — safe fallback when no config and no CLI flag.

src/tooling/docs-builder/Commands/ChangelogCommand.cs

• Resolve = shouldResolve ?? false → Resolve = shouldResolve — preserves null (unspecified) so ApplyConfigDefaults can apply the config value when the user doesn't pass either --resolve or --no-resolve.

tests/Elastic.Changelog.Tests/Changelogs/BundleChangelogsTests.cs

• Added BundleChangelogs_WithExplicitResolveFalse_OverridesConfigResolveTrue: sets resolve: true in config, passes Resolve = false to the service, and asserts the bundle contains only a file reference (not inlined content).

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

2. If you answered "Yes" to the previous question, please specify the tool(s) and model(s) used (e.g., Google Gemini, OpenAI ChatGPT-4, etc.).

Tool(s) and model(s) used: composer-1.5, claude-4.6-sonnet-medium