docs: add dual-instance planning pattern (Jon Williams)

Add vertical separation pattern (planner/implementer) as complement to horizontal scaling (Boris pattern).

## Changes

**Main guide (ultimate-guide.md)**:
- New Section 9.17.1: "Alternative Pattern: Dual-Instance Planning" (~350 lines)
  - When to use (solo devs, spec-heavy, $100-200/month)
  - Setup instructions (2 Claude instances, Plans/ directory)
  - Complete workflow (5 phases: planning, review, implementation, verification, archive)
  - Comparison table (Boris horizontal vs Jon vertical scaling)
  - Cost analysis (2 instances vs correction loops)
  - Agent-ready plan best practices
  - Limitations and tips

**Workflow file (workflows/dual-instance-planning.md)**:
- Full workflow guide (~750 lines)
- Complete example (JWT auth implementation)
- Plan template (ready to copy-paste)
- Cost breakdown and decision matrix
- Troubleshooting and bash aliases

**References updated**:
- machine-readable/reference.yaml: 15 new entries
  - dual_instance_planning, dual_instance_workflow, etc.
  - Line numbers, source attribution, metadata
- guide/workflows/plan-driven.md: Link in See Also section
- README.md: Update evaluation count (46 → 47)

**Evaluation documented**:
- docs/resource-evaluations/jon-williams-dual-instance-pattern.md
  - Full methodology (fetch, analyze, challenge, fact-check)
  - Score progression (2-3/5 → 4/5 after technical-writer challenge)
  - Gap analysis, comparison, integration rationale

## Source
LinkedIn post by Jon Williams (Product Designer, UK)
Date: 2026-02-03
URL: https://www.linkedin.com/posts/thatjonwilliams_ive-been-using-cursor-for-six-months-now-activity-7424481861802033153-k8bu

Context: Transition from Cursor (6 months) to Claude Code with Opus 4.5
Pattern: Vertical separation (Claude Zero: planning/review, Claude One: implementation)
Distinction: Orthogonal to Boris pattern (vertical vs horizontal scaling)

## Stats
- Lines added: ~1,400
- Files modified: 4
- Files created: 2 (workflow + evaluation)
- References added: 15 (reference.yaml)
- Evaluation score: 4/5 (High Value)
- Integration time: ~2.5 hours

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

machine-readable/reference.yaml

@@ -386,7 +386,7 @@ deep_dive:
   gsd_note: "Overlap with existing patterns (Ralph Loop, Gas Town, BMAD)"
   # Resource Evaluations (added 2026-01-26)
   resource_evaluations_directory: "docs/resource-evaluations/"
-  resource_evaluations_count: 46
+  resource_evaluations_count: 47
   resource_evaluations_methodology: "docs/resource-evaluations/README.md"
   resource_evaluations_appendix: "guide/ultimate-guide.md:15034"
   resource_evaluations_readme_section: "README.md:278"
@@ -452,6 +452,21 @@ deep_dive:
   multi_instance_workflows: 9583
   boris_cherny_case_study: 9617
   boris_cherny_team_patterns: 11822
+  # Dual-Instance Planning Pattern (Jon Williams, Feb 2026)
+  dual_instance_planning: 12884
+  dual_instance_workflow: "guide/workflows/dual-instance-planning.md"
+  dual_instance_overview: 12884
+  dual_instance_setup: "guide/workflows/dual-instance-planning.md:49"
+  dual_instance_complete_workflow: "guide/workflows/dual-instance-planning.md:149"
+  dual_instance_plan_template: "guide/workflows/dual-instance-planning.md:457"
+  dual_instance_cost_analysis: "guide/workflows/dual-instance-planning.md:652"
+  dual_instance_comparison: 13074  # Boris vs Jon comparison table
+  dual_instance_source: "https://www.linkedin.com/posts/thatjonwilliams_ive-been-using-cursor-for-six-months-now-activity-7424481861802033153-k8bu"
+  dual_instance_author: "Jon Williams (Product Designer, UK)"
+  dual_instance_date: "2026-02-03"
+  dual_instance_pattern: "Vertical separation (planner vs implementer) - orthogonal to Boris horizontal scaling"
+  dual_instance_cost: "$100-200/month (vs $500-1K Boris pattern)"
+  dual_instance_audience: "Solo devs, spec-heavy work, quality > speed"
   # External resource: Claude Code team tips (paddo.dev, Feb 2026)
   team_tips_paddo: "https://paddo.dev/blog/claude-code-team-tips/"
   team_tips_paddo_source: "Boris Cherny thread (x.com/bcherny/status/2017742741636321619)"