Add structural dependency analysis artifacts

- graph.json: Canonical dependency graph (10 crates, 16 edges, 76 files)
- graph.summary.md: One-page overview with fan-in/fan-out rankings
- sccs.md: Strongly Connected Components analysis (no cycles)
- layers.observed.md: 5-layer architecture diagram
- hotspots.md: Coupling hotspots (g3-config, g3-cli)
- limitations.md: Extraction limitations and validity conditions

analysis/deps/sccs.md

@@ -0,0 +1,64 @@
+# Strongly Connected Components Analysis
+
+## Summary
+
+**No cycles detected in the crate-level dependency graph.**
+
+The G3 workspace exhibits a clean DAG (Directed Acyclic Graph) structure at the crate level.
+
+## Analysis Method
+
+Cycle detection performed via manual topological sort verification of the 16 internal dependency edges.
+
+## Topological Order (Valid)
+
+The following topological ordering confirms acyclicity:
+
+1. g3-config (leaf)
+2. g3-execution (leaf)
+3. g3-computer-control (leaf)
+4. g3-providers (leaf)
+5. g3-core (depends on 1-4)
+6. g3-ensembles (depends on 1, 5)
+7. g3-planner (depends on 1, 4, 5)
+8. g3-cli (depends on 1, 4, 5, 6, 7)
+9. g3 (depends on 4, 8)
+10. g3-console (standalone)
+
+## Potential Coupling Concerns
+
+While no cycles exist, the following patterns warrant attention:
+
+### Diamond Dependencies
+
+```
+g3-cli ──────────────────────────────┐
+   │                                  │
+   ├── g3-core ── g3-config ◄─────────┤
+   │                                  │
+   ├── g3-planner ── g3-config ◄──────┤
+   │                                  │
+   └── g3-ensembles ── g3-config ◄────┘
+```
+
+`g3-config` is reached via multiple paths from `g3-cli`. This is not a cycle but indicates `g3-config` is a shared foundation.
+
+### Similar Diamond for g3-core
+
+```
+g3-cli ──────────────────────────────┐
+   │                                  │
+   ├── g3-core ◄──────────────────────┤
+   │                                  │
+   ├── g3-planner ── g3-core ◄────────┤
+   │                                  │
+   └── g3-ensembles ── g3-core ◄──────┘
+```
+
+## Module-Level Analysis
+
+Module-level cycle detection was not performed. The `use crate::` statements within each crate suggest internal module dependencies but these are expected within a single compilation unit.
+
+## Conclusion
+
+The crate dependency structure is healthy with no circular dependencies.