Default group-pull-request-title-pattern prevents release creation on merge

[zeitlinger]

Bug

When using manifest mode with separate-pull-requests: false (the
default), release-please uses group-pull-request-title-pattern to
generate the release PR title. The default pattern produces titles
like chore: release main — which does not include ${version}.

When this PR is merged, release-please cannot extract the version
from the title, so it silently skips creating the GitHub release
and tag. The manifest gets updated (indicating the release PR was
recognized), but no release is created.

Steps to reproduce

1. Use manifest config with a single package and default settings:

{
  "packages": {
    ".": {
      "release-type": "maven"
    }
  }
}

2. Release-please creates a PR titled chore: release main
3. Merge the PR
4. Release-please runs but does not create a tag or GitHub release
5. Logs show:

⚠ pullRequestTitlePattern miss the part of '${scope}'
⚠ pullRequestTitlePattern miss the part of '${component}'
⚠ pullRequestTitlePattern miss the part of '${version}'
...
⚠ Expected 1 releases, only found 0

Expected behavior

Either:

• The default group-pull-request-title-pattern should include
  ${version} (e.g. chore${scope}: release${component} ${version})
• Or the warnings about missing ${version} in the title pattern
  should be errors that prevent creating a PR that can never result
  in a release

Workaround

Explicitly set the title pattern in config:

{
  "group-pull-request-title-pattern": "chore${scope}: release${component} ${version}"
}

Context

Hit this in https://github.com/prometheus/client_java while setting
up release-please with manifest mode. Release PRs were created and
merged successfully but no releases were ever produced. Took
significant debugging to trace it to the title pattern.

Using release-please v17.1.3 via release-please-action v4.4.0.