docs: add ADR-002 integration patterns (Platinum Sprint)

Author: 4444J99

docs/adr/002-integration-patterns.md

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+# ADR-002: Cross-Organ Integration and Dependency Patterns
+
+## Status
+
+Accepted
+
+## Date
+
+2026-02-11
+
+## Context
+
+The organvm system enforces a strict dependency flow: ORGAN-I (Theory) feeds into ORGAN-II (Art), which feeds into ORGAN-III (Commerce). ORGAN-IV (Orchestration) governs all organs. No back-edges are permitted (e.g., ORGAN-III cannot depend on ORGAN-II). `sema-metra--alchemica-mundi` must define its integration points within this constraint.
+
+## Decision
+
+This repository participates in the cross-organ dependency graph as follows:
+- **Upstream dependencies**: Defined in `registry-v2.json` under the `dependencies` field
+- **Downstream consumers**: Other repos that list this repo in their dependencies
+- **Integration pattern**: NPM package consumption or API integration
+- **Communication**: Asynchronous — repos communicate through versioned releases and registry state, not runtime coupling
+
+The promotion state machine (LOCAL -> CANDIDATE -> PUBLIC_PROCESS -> GRADUATED -> ARCHIVED) governs when this repo's outputs become available to downstream consumers.
+
+## Consequences
+
+### Positive
+
+- No circular dependencies — the dependency graph is a DAG validated by CI
+- Loose coupling allows independent development and deployment
+- Registry-driven discovery makes integration points explicit
+
+### Negative
+
+- Cross-organ changes require coordinated registry updates
+- Promotion gates may slow down rapid iteration during prototyping
+
+## References
+
+- Dependency validation: `validate-dependencies.yml` in [orchestration-start-here](https://github.com/organvm-iv-taxis/orchestration-start-here)
+- Organ: ORGAN-I (Theoria)
+- Orchestration system: `docs/implementation/orchestration-system-v2.md`