Update blowdryer-diffplug to 9.1.0 to fix publishing

[nedtwigg]

Fixes the failed deploy in run 32311994888:

> Task :initializeSonatypeStagingRepository FAILED
> Failed to load staging profiles, server at https://s01.oss.sonatype.org/service/local/
  responded with status code 402

We were pinned to blowdryer-diffplug 9.0.0, whose base/sonatype.gradle still points at s01.oss.sonatype.org. That host is dead — 9.0.4 moved to the central portal urls.

Changes

• blowdryer-diffplug 9.0.0 → 9.1.0 — picks up the sonatype url fix (9.0.4), the changelogBumpFreshmarkGitAdd Gradle-9 warning fix (9.0.5), and the spotless deprecation fixes (9.0.1/9.0.2).
• Plugins block synced to 9.1.0's plugin.versions — spotless 7.0.3 → 7.2.1, plus com.gradle.develocity 4.1.1. Required; setPluginsBlockTo fails the build on mismatch.
• base/buildscan-on-ci.gradle applied — the 9.1.0 feature the develocity plugin is there for. Scans publish only when CI is set. Matches goomph's settings.gradle.
• secrets.GH_TOKEN → secrets.GITHUB_TOKEN in deploy.yml. The deploy died before reaching the GitHub-release step so the PAT was never exercised, but it was last set 2024-01-23 and goomph needed this same swap to get green after the sonatype migration. Repo workflow permissions are already write, and changelogPush targets release, not protected main.

Deploy stays on JVM 11 (goomph moved to 17) because this repo's build.gradle disables spotlessFreshmark on Java 12+, and changelogBumpFreshmark needs to run to bump the README version links.

Gradle wrapper left at 8.10.2 — goomph publishes fine on 8.10.1.

Verification

./gradlew build configures cleanly and all tests pass except BlowdryerPluginTest.tooOldError, which fails identically on unmodified main: it drives Gradle 6.7 through TestKit, and 6.7's Groovy can't read Java 21 class files (Unsupported class file major version 65). Its Assume only guards Java 17, so it's a local-JDK artifact — CI runs 11 and 17. The 'indentWithSpaces' is deprecated warnings from the failed run are gone.

The failed run left nothing to clean up: main and release were both at 3f631cc, and no release/1.7.2 tag was created.

🤖 Generated with Claude Code

https://claude.ai/code/session_011wHkSPGLE7g451CaG9q1nD