ci: inline LPP integration tests into the workflow

[Teakowa]

Summary

Follow-up to #405, continuing the work of making CI steps plain single commands.

scripts/test-lpp-integration.sh only ran three cargo test targets. The LPP integration job now runs them directly as a single command, and the wrapper script is removed:

run: >-
  cargo test --locked -p wright-lpp -p wright-driver
  --test mock_provider --test lpp --test provider_edit

The LPP_MOCK_PROVIDER env and the job's triggers are unchanged.

Validation

• Locally, the single command runs exactly the three targets: lpp (4 passed), provider_edit (11 passed) and mock_provider (14 passed).
• Locally the suites self-skip their mock-provider cases because LPP_MOCK_PROVIDER is unset. This PR's CI runs them against the built mock provider.
• The workflow YAML parses, git diff --check is clean, and nothing else references the removed script.

🤖 Generated with Claude Code

https://claude.ai/code/session_0178vQfKDP4QsRd2Kykm3FZ4

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