Fix Renovate bundler update failures (rangeStrategy) and invalid manager rule

[kimadactyl]

Problem

Renovate has been failing on this repo with a persistent repository problem on the Mend dashboard:

⚠️ WARN: Error updating branch: update failure

Two bundler branches fail on every run:

• renovate/pin-dependencies — pinning axe-core-rspec ('~> 4.8' → 4.11.3)
• renovate/ruby-on-rails-packages — pinning rails ('~> 8.0' → 8.1.3)

Root cause

renovate.json sets "rangeStrategy": "pin" globally. That's fine for npm (those updates succeed), but for the bundler manager it tries to rewrite the Gemfile's pessimistic constraints (e.g. gem 'rails', '~> 8.0') into exact versions inside the Gemfile. Renovate's bundler manager can't do that replacement — it logs Value is not updated → Error updating branch: update failure. Because the failure happens at the file-update stage (before any bundle lock), the branches never get created and the dashboard stays red.

Fix

Override rangeStrategy to update-lockfile for the bundler manager only. For a Rails application, the idiomatic approach is to keep loose constraints in the Gemfile and let Gemfile.lock carry the exact pinned versions. update-lockfile updates the lockfile and only edits the Gemfile when a new version falls outside the existing range. pin still applies to npm and every other manager, so nothing else changes.

Bonus fix

While validating, renovate-config-validator flagged a second, pre-existing error: the minimumReleaseAge rule used matchManagers: ["npm", "rubygems"], but rubygems is a datasource, not a manager (the Ruby manager is bundler). The rule was invalid, so the 7-day release-age delay wasn't reliably applying to Ruby gems. Switched to matchDatasources: ["npm", "rubygems"] — which is what those values were always meant to be — so the delay now correctly covers both npm packages and Ruby gems.

Verification

renovate-config-validator passes:

 INFO: Validating renovate.json
 INFO: Config validated successfully

(Before this change it reported Configuration Error … You have included an unsupported manager in a package rule. Your list: npm,rubygems.)

prettier --check renovate.json is clean.