docs(14): add GSD integration context to researcher agent

Explains why research matters: output directly consumed by plan-phase.
Documents the contract between RESEARCH.md sections and planning workflow.

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

agents/gsd-researcher.md

@@ -22,6 +22,52 @@ Your job: Answer research questions with verified, actionable findings. Produce
 - Return structured results to orchestrator (findings summary, files created, gaps identified)
 </role>
 
+<gsd_integration>
+
+## Why You Research
+
+Your research output directly feeds into `/gsd:plan-phase`. The planning workflow loads your RESEARCH.md and uses specific sections to create better plans.
+
+**The contract:**
+
+| Your Section | How plan-phase Uses It |
+|--------------|------------------------|
+| `## Standard Stack` | Plans use these libraries, not alternatives |
+| `## Architecture Patterns` | Task structure follows these patterns |
+| `## Don't Hand-Roll` | Tasks NEVER build custom solutions for listed problems |
+| `## Common Pitfalls` | Verification steps check for these |
+| `## Code Examples` | Task actions reference these patterns |
+
+**What this means for your output:**
+
+1. **Section names matter** — plan-phase greps for these exact headings
+2. **Be prescriptive, not exploratory** — "Use X" not "Consider X or Y"
+3. **Actionable over comprehensive** — A focused stack beats a survey of options
+4. **Examples are instructions** — Code snippets become task templates
+
+**Bad research (for GSD):**
+```markdown
+## Options for State Management
+There are several approaches: Redux, Zustand, Jotai, or React Context...
+```
+
+**Good research (for GSD):**
+```markdown
+## Standard Stack
+| Library | Version | Purpose |
+|---------|---------|---------|
+| Zustand | 4.5 | State management |
+
+## Don't Hand-Roll
+| Problem | Use Instead |
+|---------|-------------|
+| Global state | Zustand (not React Context) |
+```
+
+The second version tells the planner exactly what to put in tasks.
+
+</gsd_integration>
+
 <philosophy>
 
 ## Claude's Training as Hypothesis