feat(oxlint/lsp): report malformed suppression baselines - #26543

Summary

• Reports malformed oxlint-suppressions.json baselines to the LSP client.
• Preserves warning logs and fail-open lint behavior.
• Adds a focused builder test for the client message.

Dependencies

This is a stacked follow-up to #25093. Keep it in draft until both dependencies land:

• feat(oxlint/linter/lsp): apply bulk suppression baseline #25093
• feat(oxlint/lsp): show config errors to LSP client #25486

After both merge, rebase this branch onto main and verify the final integration before marking it ready.

Test plan

• cargo test -p oxlint test_malformed_suppression_file_returns_client_message
• cargo fmt -- --check

AI assistance

Prepared with Codex. The author remains responsible for reviewing, understanding, and validating the change.