fix(release): bump every train coordinate in the root README

[DemchaAV]

Why

v2.4.0 shipped a README whose graph-compose-testing snippet read 2.3.0 beside graph-compose 2.4.0. The testing snippet arrived with #690, and the release commit bumped only the bare graph-compose coordinate:

• Update-ReadmeInstallVersion rewrote the first graph-compose Maven and Gradle match, and nothing else.
• VersionConsistencyGuardTest read the root README the same way.

The train is a tested-compatible set only at one version, so a reader following that page mixed two releases, with every gate green.

What changed

• scripts/cut-release.ps1: the root README bump rewrites every graph-compose* coordinate, Maven and Gradle, and skips graph-compose-fonts and graph-compose-emoji. Update-ModuleReadmeInstallVersion already applies that rule to module READMEs and docs pages. The legacy JitPack fallback is unchanged.
• VersionConsistencyGuardTest: readmeInstallSnippetsMatchTheProjectVersion keeps its graph-compose Maven and Gradle assertions.
  • It now also holds every GraphCompose coordinate on the page to the train version, and a companion to its own pom.
  • It reuses the coordinate scan from the docs/ check, extracted as coordinatesIn and driftIn. The docs check behaves as before.
• .github/workflows/release-script-check.yml: a new unit check lifts Update-ReadmeInstallVersion by AST, like the checks around it, and asserts that something calls it. It then runs the function twice:
  • on a fixture, against an exact expected text: graph-compose and graph-compose-testing move, fonts and emoji stay, and a second run changes nothing;
  • on a copy of the real README: no train coordinate is left behind and no other line changes.
• README.md: the graph-compose-testing snippet reads 2.4.0.
• docs/contributing/release-process.md: §1 step 2 now says what the root README pass rewrites.

Verification

• Before the README fix: VersionConsistencyGuardTest failed with README.md:196 graph-compose-testing advertises 2.3.0, expected one of [2.4.0]. After it, 23/23 pass.
• Documentation guards: ./mvnw -B -ntp test -pl :graph-compose-core -Dtest=com.demcha.documentation.** gives BUILD SUCCESS with 145 tests. That includes the guards that parse cut-release.ps1: ReleaseAssetStepGuardTest, ReleaseKnowledgeGateGuardTest, ReleaseScriptGitExitCodeGuardTest, ReleaseScriptInstallListGuardTest and ReleaseScriptRoadmapGuardTest.
• The new workflow step, run locally from the workflow file:
  • it passes on this branch, checking 3 README coordinates;
  • against a copy of the script with the bare-coordinate regexes restored, it fails with "the fixture did not bump to its expected text".
• Dry run: cut-release.ps1 -Version 2.4.99 -Branch develop -DryRun -SkipShowcase exits 0 and reports the README Maven and Gradle bumps.
• Hygiene: the script parses with 0 errors, and git diff --check is clean.

Lane: build. Covers the release script, its CI check, one guard test and two documentation lines; no library code.