Localizer integration: end-to-end test executing the CLI commands on real project data

[gildor]

Background

The plugin delegates all localization work to the bandlab-localizer CLI (LocalizerOps):

• update-strings (full sync)
• update-strings --update-keys <keys>
• update-strings --add-keys <keys> --target-file <path>
• update-strings --delete-keys <keys>

Localizer 3.2.0 renamed --add-keys-to-file → --target-file (localizer #152). The plugin kept
emitting the old flag and nothing failed in CI — no test asserts the argv we send to the CLI.

Done already (flag-surface contract)

LocalizerCliContractTest now asserts every flag the plugin emits is a recognised update-strings
option, via update-strings --help — no network, no Tolgee creds. It runs against the localizer jar
pinned to the version the app's wrapper uses (LOCALIZER_JAR, currently 3.2.0) and self-skips when
that env var is unset, so the default hermetic ./gradlew test is unaffected. This would have caught
the rename instantly.

This issue: real end-to-end execution

Go beyond the --help surface and actually run the commands against real-shaped project data, so
we catch behavioural drift (output format, exit codes, [[file]] routing), not just flag names.

Proposed shape

• Fixture from bandlab-android. Copy a small, realistic slice: the bandlab-localizer wrapper
  pinned to the app's version, a bandlab-localizer-config.toml, and a couple of [[file]] entries
  with their base + translation strings.xml. ⚠️ Scrub the Tolgee api-key from the copied
  config — the real one must not be committed; use a dummy / ${TOLGEE_API_KEY} interpolation.
• Creds-free path (always runs when a jar is available): execute update-strings --delete-keys <key>
  on the fixture and assert the key is removed from the base file and every translation, exit 0.
  Delete needs zero network/creds.
• Tolgee path (opt-in, gated on a live key): --add-keys … --target-file, --update-keys, and
  full sync hit Tolgee. Run these against keys copied from the Android project when TOLGEE_API_KEY
  is present; skip otherwise.
• Gating: a separate tagged task / source set, off by default and excluded from check, so the
  hermetic ./gradlew test and normal CI stay green. Optionally a dedicated CI job that builds the
  localizer jar (or pulls the pinned release) and runs it.

Acceptance

• Fixture copied from bandlab-android with the api-key scrubbed.
• --delete-keys executed end-to-end; asserts removal from base + all translations.
• add/update/full-sync executed when TOLGEE_API_KEY is set; skipped cleanly otherwise.
• Lives behind a separate task; default ./gradlew test unchanged.

Follow-up to the --target-file fix and LocalizerCliContractTest. Relates to #214.