chore: add project documentation framework

.project-docs/20-architecture/data-flow.md

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+# Data Flow
+
+## Primary Flows
+
+| Flow | Source | Destination | Notes |
+|---|---|---|---|
+
+## State Ownership
+
+- {state owner or persistence rule}
+
+## External Interfaces
+
+- {API, file, service, or user-facing boundary}
+
+## Last Updated
+
+{YYYY-MM-DD}

.project-docs/20-architecture/module-map.md

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+# Module Map
+
+## Source Layout
+
+| Path | Responsibility | Owner Notes |
+|---|---|---|
+
+## Dependency Direction
+
+- {dependency direction rule}
+
+## Risky Or Sensitive Areas
+
+- {module or path that needs extra care}
+
+## Last Updated
+
+{YYYY-MM-DD}

.project-docs/20-architecture/system-overview.md

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+# System Overview
+
+## Current Architecture
+
+{short description of the current system shape}
+
+## Main Components
+
+| Component | Responsibility | Notes |
+|---|---|---|
+
+## Important Boundaries
+
+- {boundary that future work should respect}
+
+## Related Decisions
+
+- {ADR reference}
+
+## Last Updated
+
+{YYYY-MM-DD}