test: add coverage for helper dispatch and service alias resolution

[Bortlesboat]

Summary

• Add unit tests for helpers::get_helper() — previously untested
• Expand services::resolve_service() test coverage with edge cases

New Tests

helpers/mod.rs

• test_get_helper_known_services — all 11 service names return a helper
• test_get_helper_unknown_returns_none — unknown/empty/wrong-case returns None
• test_get_helper_script_alias — both "script" and "apps-script" work
• test_helper_default_not_helper_only — default trait impl returns false

services.rs

• test_resolve_service_all_aliases — exhaustively tests every alias in SERVICES
• test_resolve_service_case_sensitive — "Drive" and "GMAIL" should fail
• test_resolve_service_empty_string — empty string should fail
• test_resolve_service_error_lists_known_services — error message includes available services
• test_no_duplicate_aliases — ensures no alias appears twice in SERVICES

Test plan

• cargo test passes (CI will verify)
• cargo clippy -- -D warnings clean (CI will verify)

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[changeset-bot]

🦋 Changeset detected

Latest commit: 9340f25

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@googleworkspace/cli	Patch

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[Bortlesboat]

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[jpoehnelt]

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[jpoehnelt]

test failure