Improve PIR depth blast radius detection feedback

[danyili2632]

Summary

• add root cause scope, recurrence likelihood, recurrence prevention evidence, and RCA depth scoring
• add blast radius metrics for affected systems, records/secrets, business impact, cost, regulatory notification, and third-party impact
• add detection engineering feedback loop and communication coordination assessment sections
• add pitfall guidance for fixing one instance instead of the recurring failure pattern

Bounty

Addresses #1534.

I have read and agree to the CONTRIBUTING.md bounty terms. Preferred payment method can be provided privately after maintainer acceptance.

Validation

• git diff --check