Bug: pm close validation warnings for resolution fields on items that are straightforward duplicates #160

Summary

When closing duplicate items with pm close <id> "reason", the CLI produces warnings like close_validation_missing_fields:resolution,expected_result,actual_result. For simple duplicate closures, requiring resolution/expected_result/actual_result is overly strict for what is essentially a "duplicate of X" closure.

Reproduction

pm close pm-a5c5 "Duplicate of INFRA-002 (pm-hpvo). Consolidating into single tracker item."
# Output includes:
# warnings:
#   - close_validation_missing_fields:pm-a5c5:resolution,expected_result,actual_result

Expected Behavior

For items closed with a clear reason that references a duplicate (e.g., contains "Duplicate of" or "merged into"), the validation should either:

1. Not warn about missing resolution/expected/actual fields, OR
2. Auto-populate them from the referenced item, OR
3. Provide a --skip-resolution flag for trivial closures

Suggested Fix

Add a --close-reason duplicate or --duplicate-of <id> flag that auto-populates resolution fields:

• resolution: "Duplicate of <referenced_id>"
• expected_result: "Consolidated into <referenced_id>"
• actual_result: "Consolidated into <referenced_id>"