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/hotspots.md

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+# Coupling Hotspots
+
+## High Fan-In Nodes
+
+Nodes with disproportionate incoming dependencies (dependents).
+
+| Crate | Fan-In | % of Crates | Classification |
+|-------|--------|-------------|----------------|
+| g3-config | 5 | 50% | **High** - shared foundation |
+| g3-core | 4 | 40% | **High** - central hub |
+| g3-providers | 4 | 40% | **High** - shared foundation |
+| g3-cli | 1 | 10% | Normal |
+| g3-execution | 1 | 10% | Normal |
+| g3-computer-control | 1 | 10% | Normal |
+| g3-ensembles | 1 | 10% | Normal |
+| g3-planner | 1 | 10% | Normal |
+
+### g3-config (Fan-In: 5)
+
+**Dependents:** g3-cli, g3-core, g3-ensembles, g3-planner, (implicit: g3)
+
+**Evidence:**
+- `g3-cli/Cargo.toml`: `g3-config = { path = "../g3-config" }`
+- `g3-core/Cargo.toml`: `g3-config = { path = "../g3-config" }`
+- `g3-ensembles/Cargo.toml`: `g3-config = { path = "../g3-config" }`
+- `g3-planner/Cargo.toml`: `g3-config = { path = "../g3-config" }`
+
+**Coupling Pattern:** Configuration struct (`Config`) is passed through the call stack. Changes to `Config` fields propagate to all dependents.
+
+### g3-core (Fan-In: 4)
+
+**Dependents:** g3-cli, g3-ensembles, g3-planner
+
+**Evidence:**
+- `g3-cli/Cargo.toml`: `g3-core = { path = "../g3-core" }`
+- `g3-ensembles/Cargo.toml`: `g3-core = { path = "../g3-core" }`
+- `g3-planner/Cargo.toml`: `g3-core = { path = "../g3-core" }`
+
+**Coupling Pattern:** `Agent` struct is the primary interface. Feature modules create and orchestrate agents.
+
+### g3-providers (Fan-In: 4)
+
+**Dependents:** g3, g3-cli, g3-core, g3-planner
+
+**Evidence:**
+- `Cargo.toml`: `g3-providers = { path = "crates/g3-providers" }`
+- `g3-cli/Cargo.toml`: `g3-providers = { path = "../g3-providers" }`
+- `g3-core/Cargo.toml`: `g3-providers = { path = "../g3-providers" }`
+- `g3-planner/Cargo.toml`: `g3-providers = { path = "../g3-providers" }`
+
+**Coupling Pattern:** `Message`, `MessageRole`, `LLMProvider` trait are widely used types.
+
+## High Fan-Out Nodes
+
+Nodes with disproportionate outgoing dependencies.
+
+| Crate | Fan-Out | % of Crates | Classification |
+|-------|---------|-------------|----------------|
+| g3-cli | 5 | 50% | **High** - orchestrator |
+| g3-core | 4 | 40% | **High** - integrator |
+| g3-planner | 3 | 30% | Moderate |
+| g3-ensembles | 2 | 20% | Normal |
+| g3 | 2 | 20% | Normal |
+
+### g3-cli (Fan-Out: 5)
+
+**Dependencies:** g3-core, g3-config, g3-planner, g3-providers, g3-ensembles
+
+**Coupling Pattern:** CLI orchestrates all major features. This is expected for a top-level UI crate.
+
+### g3-core (Fan-Out: 4)
+
+**Dependencies:** g3-providers, g3-config, g3-execution, g3-computer-control
+
+**Coupling Pattern:** Core integrates all foundation crates. This is the expected role of a "core" module.
+
+## File-Level Hotspots
+
+### g3-core/src/lib.rs
+
+**Lines:** ~3366 (largest file in codebase)
+
+**Concerns:**
+- Contains the entire `Agent` struct implementation
+- High cyclomatic complexity
+- Multiple responsibilities (streaming, tools, context management)
+
+**Evidence:** File contains 19 public module declarations and the main `Agent` implementation.
+
+### g3-cli/src/lib.rs
+
+**Lines:** ~2888
+
+**Concerns:**
+- Contains multiple mode implementations (autonomous, interactive, planning, agent)
+- Large `run_autonomous` function
+- Mixed concerns (UI, orchestration, error handling)
+
+## Cross-Crate Type Dependencies
+
+### Most Shared Types
+
+| Type | Defined In | Used By |
+|------|------------|--------|
+| `Config` | g3-config | g3-cli, g3-core, g3-ensembles, g3-planner |
+| `Message` | g3-providers | g3-core, g3-cli, g3-planner |
+| `MessageRole` | g3-providers | g3-core, g3-cli, g3-planner |
+| `Agent` | g3-core | g3-cli, g3-ensembles, g3-planner |
+| `LLMProvider` | g3-providers | g3-core, g3-planner |
+| `UiWriter` | g3-core | g3-cli |
+
+## Metrics Summary
+
+| Metric | Value | Threshold | Status |
+|--------|-------|-----------|--------|
+| Max Fan-In | 5 (g3-config) | ≤6 | ✅ OK |
+| Max Fan-Out | 5 (g3-cli) | ≤6 | ✅ OK |
+| Largest File | 3366 lines | ≤1000 | ⚠️ Large |
+| Crates with Fan-In > 3 | 3 | ≤4 | ✅ OK |
+| Crates with Fan-Out > 3 | 2 | ≤3 | ✅ OK |