investigate: ignore.rules does not filter security scanner findings from SARIF output #326

Problem

.cora.yaml ignore.rules with pattern "Command injection via exec/system with dynamic input" does not filter out findings from the built-in security_scanner (injection/exec rule). SARIF output still contains the finding even though:

1. apply_ignore_rules() in review.rs:341 runs after merge_rule_findings() at line 311
2. The RuleFinding title matches the ignore pattern via contains()
3. .cora.yaml is correctly detected and loaded in CI log

Evidence

• SARIF output: 3201 bytes, 1 finding despite ignore rule
• CI log: No blocking issues (severity filter works, but SARIF still has the finding)
• Cora CLI version: v0.6.2

Suspected Cause

Possibly a config merge ordering issue where ignore rules are applied but the SARIF formatter receives the pre-filtered response rather than the filtered one. Or the security_scanner findings are re-added after ignore rules are applied.

Files to Investigate

• src/engine/review.rs:302-341 (merge + filter ordering)
• src/engine/security_scanner.rs (finding generation)
• src/engine/rules/mod.rs:109-145 (merge_rule_findings, sets issue_type: rule)
• src/commands/review.rs:263 (filtered_response = response.clone)