fix(lint): mark truncated parse fallbacks

[fengjikui]

Summary

Follow-up to #2204 for the lint fallback paths that still used silent character truncation when structured output parsing failed.

• use the existing passthrough truncation marker for Ruff JSON parse failures
• use the existing passthrough truncation marker for golangci-lint JSON parse failures
• add regression tests so long malformed JSON output visibly reports [RTK:PASSTHROUGH] Output truncated

This does not overlap with #2205, which focuses on git log output.

Validation

• cargo fmt --check
• cargo test cmds::python::ruff_cmd::tests
• cargo test cmds::go::golangci_cmd::tests
• cargo clippy --all-targets -- -D warnings
• cargo test

AI assistance

I used Codex to help prepare this patch, reviewed the diff, and ran the validation commands above locally.

[CLAassistant]

All committers have signed the CLA.