[BUG] Requirement Validation Fails When Metadata Fields Precede Description #418

The requirement SHALL/MUST validation incorrectly checks metadata fields instead of the requirement description, causing false validation failures on valid requirements.

Steps to Reproduce

• Create a spec file with a requirement that includes metadata fields immediately after the title:

  ### Requirement: File Serving
  **ID**: REQ-FILE-001
  **Priority**: P1
  
  The system MUST serve static files from the root directory.
  

• Run validation on the spec file
• Observe validation failure despite the requirement containing proper normative keywords (MUST)

Expected Behavior

The validator should:

• Skip metadata field lines (matching pattern /^\*\*[^*]+\*\*:/)
• Check the actual requirement description for SHALL/MUST keywords
• Pass validation since the description contains "MUST"

Actual Behavior

The validator:

• Extracts the first non-empty line after the requirement header
• Returns ID: REQ-FILE-001 as the "requirement text"
• Fails validation because this metadata field doesn't contain SHALL/MUST
• Ignores the actual requirement description

Root Cause

The extractRequirementText() method in src/core/validation/validator.ts collects all lines after the requirement header, joins them, and returns the first non-empty line. It doesn't skip metadata field lines before extracting the normative description.

Impact

• Severity: Medium-High
• Users cannot use metadata fields in requirements without triggering false validation failures
• Blocks adoption of structured requirement metadata
• Valid, well-formed requirements are incorrectly flagged as invalid
• No workaround exists other than removing metadata fields or placing them after the description

Environment

• Affected component: cli-validate spec
• File: src/core/validation/validator.ts
• Method: extractRequirementText()