Add liquibase TOML filter

[s2005]

Summary

• add a built-in liquibase TOML filter
• support filters that merge stderr into filtered output
• register liquibase in discover rules and document the new filter field

Verification

• cargo test --all
• cargo run -- verify --filter liquibase

[CLAassistant]

All committers have signed the CLA.

[pszymkowiak]

[w] wshm · Automated triage by AI

📊 Automated PR Analysis

✨ Type	feature
🟡 Risk	medium

Summary

Adds a new built-in liquibase TOML filter that strips banners, ASCII art, and verbose info logs from liquibase CLI output. Introduces a filter_stderr field so filters can capture and merge stderr into stdout before filtering, which is needed for tools like liquibase that emit noise to stderr. Also registers liquibase in the discover rules and documents the new field.

Review Checklist

• Tests present
• Breaking change
• Docs updated

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Analyzed automatically by wshm · This is an automated analysis, not a human review.

[pszymkowiak]

Rebased on develop to clear the Cargo.toml / Cargo.lock / CHANGELOG / manifest noise — PR is now clean (1 commit, 5 files, feature-only).

Tested locally with a mock liquibase binary emitting banner on stderr:

Test	Result
rtk verify --filter liquibase	4/4 passed
Real execution (raw → filtered)	705 bytes → 133 bytes (90% savings)
Empty output	liquibase: ok
Error with exit 1	Error visible, exit code propagated

The filter_stderr field is a solid addition — it's a generic feature that will help other JVM tools (Maven, Gradle, Ant) that emit banners to stderr. Default is false, so no impact on existing filters.

LGTM — good to merge.