feat: add methodology artifact type with consumption mechanisms (#1488) (#1609)

* test(#1488): add failing tests for methodology artifact type

- Test artifact-types.md exists with methodology type documented
- Test shape, lifecycle, location fields are present
- Test discuss-phase-assumptions.md consumes METHODOLOGY.md
- Test pause-work.md Required Reading includes METHODOLOGY.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* feat(#1488): add methodology artifact type with consumption mechanisms

- Create get-shit-done/references/artifact-types.md documenting all GSD
  artifact types including the new methodology type
- Methodology artifact: standing reference of named interpretive lenses,
  located at .planning/METHODOLOGY.md, lifecycle Created → Active → Superseded
- Add load_methodology step to discuss-phase-assumptions.md so active lenses
  are read before assumption analysis and applied to surfaced findings
- Add METHODOLOGY.md to pause-work.md Required Reading template so resuming
  agents inherit the project's analytical orientation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

get-shit-done/workflows/pause-work.md

@@ -142,6 +142,7 @@ last_updated: [timestamp from current-timestamp]
 ## Required Reading (in order)
 <!-- List documents the resuming agent must read before acting -->
 1. [document] — [why it matters]
+1. `.planning/METHODOLOGY.md` (if it exists) — project analytical lenses; apply before any assumption analysis
 
 ## Critical Anti-Patterns (do NOT repeat these)
 <!-- Mistakes discovered this session that must be structurally avoided -->