[Bug]: Confidence threshold filtering inconsistent due to case mismatch (semantic findings)

[Ty-Robb]

Summary

Confidence normalization appears inconsistent across engines.

Semantic integration emits lowercase confidence (e.g., medium), while config threshold logic expects uppercase keys (LOW, MEDIUM, HIGH). This can cause confidence-threshold filtering to mis-handle semantic findings.

Affected Files

• src/semantic-integration.js
• src/config.js

Reproduction

1. Produce a semantic finding with confidence: "medium".
2. Set .scannerrc confidence threshold to MEDIUM.
3. Observe filtering can treat semantic confidence as unknown/lowest.

Expected

• Confidence values are normalized before threshold checks.
• Threshold behavior is consistent for AST/regex/semantic findings.

Suggested Fix

• Normalize confidence to uppercase at ingestion boundary.
• Add tests for mixed-case values (medium, Medium, MEDIUM).

Acceptance Criteria

• Semantic findings respect configured confidence thresholds identically to other engines.
• Unit tests cover normalization and threshold behavior.