#239 extension quality/fmt fail on pulled extensions (path mismatch)

Bug

swamp extension quality and swamp extension fmt fail when pointed at a pulled extension's manifest because they resolve model file paths relative to extensions/models/ in the repo root, not relative to the manifest file's actual location.

Reproduction

# Pull an extension
swamp extension pull @bixu/wheelshop

# Try to score it
swamp extension quality .swamp/pulled-extensions/@bixu/wheelshop/manifest.yaml --json
# Error: Model file not found: wheelshop.ts (expected at /tmp/swamp-million/extensions/models/wheelshop.ts)

# The actual file exists at:
# .swamp/pulled-extensions/@bixu/wheelshop/models/wheelshop.ts

Expected Behavior

extension quality and extension fmt should resolve model file paths relative to the manifest location (or the extension root), not hardcoded to extensions/models/ in the repo root.

Use Case

Agents evaluating pulled extensions before using them in workflows. The quality rubric is valuable for agent decision-making (should I use this extension?), but it currently only works on locally-authored extensions, not pulled ones.

Environment

• swamp version: 20260504.233645.0-sha.430c1535
• Extension: @bixu/wheelshop 2026.05.04.3