Runtime logging: filter non-actionable agent artifact churn

[jafreck]

Problem

• Logs are noisy with repeated "produced new file" events for transient or infrastructure artifacts (.git, target, Cargo.lock, etc.), making debugging harder.

Proposal

• Add configurable artifact allow/deny filters for event emission.
• Downgrade or suppress known-noise artifacts by default.
• Preserve full detail in debug mode while keeping normal logs concise.

Acceptance Criteria

• Default logs suppress repetitive non-actionable artifact events.
• Debug mode can still emit full artifact details.
• Add tests for artifact event filtering behavior.

Context reference

• Migration logs include high-volume repeated artifact creation messages that obscure failure signals.