ci: resolve release dependency checks against in-repo packages

[leoafarias]

Problem

Protocol / Release dependency check and Winds / Release dependency check resolve mix_protocol and mix_winds against the published pub.dev Mix, then analyze and test them. This blocks any PR that changes packages/mix together with the dependents that need the change. For example, #1072 adds BlurModifierMix.tileMode:

• Without the matching mix_protocol codec update, the main test job fails, because mix_protocol checks each styler's field count against a fixed list.
• With the update, the protocol release check fails, because tileMode does not exist in the published mix 2.2.0.

No version of that PR can pass both jobs. After such a change merges, main stays red on this job until Mix is released.

Change

In .github/workflows/test.yml, both release-dependency jobs now:

• write a pubspec_overrides.yaml that points mix, mix_annotations, and (for winds) mix_protocol at the repository. Winds also gets one for its example. They still run a plain flutter pub get without Melos, then analyze and test the package on its own.
• use flutter analyze --no-fatal-infos, matching melos run analyze:dart. Deprecations in unreleased Mix (for example feat(mix): deprecate styler convenience shorthands #1063) show up as infos in dependents.
• remove the overrides before dart pub publish --dry-run, so the dry run still resolves the declared constraints (mix: ^2.2.0) against pub.dev.
• skip the override step when the workflow is run manually (workflow_dispatch) with published_deps: true. That run checks against pub.dev only, which is the old behavior.

Where the published-dependency guarantee is enforced now

• At publish time (blocking): publish.yml calls btwld/dart-actions. That workflow runs a plain flutter pub get (overrides are gitignored and never checked in), flutter test, and dart pub publish --dry-run, all before publishing. A dependent that needs unreleased Mix fails there and is not published.
• Before tagging (on demand): run Test Workflow manually with published_deps enabled to get the old pub.dev-only check.
• On every PR: the publish dry run still validates the archive and that the declared constraints resolve on pub.dev.

Examples / Published Mix is left as it is. Keeping the showcase working with published Mix is deliberate there.

Verification

• actionlint .github/workflows/test.yml passes.
• I simulated both jobs locally on a clean export of the feat(mix): support blur tileMode across core and protocol #1072 branch, with no Melos overrides:
  • mix_protocol: analysis passes (9 infos), 405 tests pass.
  • mix_winds: analysis passes with no issues, 824 tests pass.
  • Both resolve mix, mix_annotations, and mix_protocol from the repo paths.
• dart pub publish --dry-run on mix_protocol without overrides: 0 warnings.

[tilucasoli]

LGTM!