feat(known-error): support multiple regex patterns per known error

[rubberduck203]

Summary

• spec.pattern now accepts either a single string (existing behavior, unchanged) or a list of strings
• A log line matching any one of the patterns triggers the known error
• An empty list is rejected at both the schema layer and at parse time
• Internally, patterns are compiled into a RegexSet for single-pass matching

Details

Uses a #[serde(untagged)] enum (KnownErrorPattern) to accept both forms under the same pattern key — the same idiom already used by SkipSpec in this codebase. Single-string configs round-trip unchanged; no migration needed.

# still works
spec:
  pattern: "No space left on device"

# now also works
spec:
  pattern:
    - "No space left on device"
    - "Out of memory"

Implementation notes

• Schema: the Many variant carries minItems: 1 via a schema_with helper, so schema-aware tooling (IDE validators, YAML linters) catches pattern: [] at authoring time. A runtime guard in TryFrom remains as defense-in-depth since validate_resource only warns on schema mismatches.
• Internal model: the old parallel patterns: Vec<String> / regexes: Vec<Regex> fields are replaced by a single regexes: RegexSet. RegexSet matches all patterns in one DFA pass and exposes the original strings via .patterns(), eliminating the dual-storage issue.
• Also includes a pre-existing clippy lint fix (useless_vec → array literal in a test) that would otherwise fail CI under -D warnings.

Test plan

• cargo test — all existing tests pass (backward compatibility)
• New unit tests: parses_list_of_patterns, empty_pattern_list_is_rejected, try_from_multi_pattern_spec
• schema_rejects_empty_pattern_list — confirms pattern: [] is caught at the schema layer
• cargo test create_and_validate_schemas — regenerated schemas validated against both single-string and multi-pattern example fixtures
• cargo clippy --all-targets --all-features -- -D warnings — clean

🤖 Generated with Claude Code

[ivy]

Nice job on the backwards compatibility!