Remove redundant 'No plan exists' message from plan_read output

The UI already shows 'empty' via print_plan_compact, so returning an
empty string avoids duplicate output.

analysis/deps/sccs.md

@@ -1,27 +1,83 @@
 # Strongly Connected Components (Cycles)
 
+**Generated**: 2025-02-02  
+**Method**: Manual analysis of crate and file-level dependency graph
+
+## Crate-Level Cycles
+
+**None detected.**
+
+The crate dependency graph is a DAG (directed acyclic graph). All crate dependencies flow downward:
+
+```
+g3-cli → g3-core → g3-providers
+       → g3-config
+       → g3-planner → g3-core (creates diamond, not cycle)
+                    → g3-providers
+                    → g3-config
+       → g3-computer-control
+       → g3-providers
+
+g3-core → g3-execution
+        → g3-computer-control
+```
+
+## File-Level Cycles Within Crates
+
+### g3-core
+
+**Potential cycle via lib.rs re-exports:**
+
+Multiple modules import from `lib.rs` (for `ToolCall`, `Agent`, etc.), and `lib.rs` declares these modules. This is standard Rust module structure, not a problematic cycle.
+
+```
+lib.rs ←──mod──→ streaming_parser.rs (uses crate::ToolCall)
+lib.rs ←──mod──→ context_window.rs (uses crate::ToolCall)
+lib.rs ←──mod──→ acd.rs (uses crate::ToolCall)
+lib.rs ←──mod──→ streaming.rs (uses crate::ToolCall)
+lib.rs ←──mod──→ stats.rs (uses crate::CacheStats)
+lib.rs ←──mod──→ retry.rs (uses crate::{Agent, DiscoveryOptions, TaskResult})
+lib.rs ←──mod──→ feedback_extraction.rs (uses crate::{Agent, TaskResult})
+```
+
+This is the standard Rust pattern where `lib.rs` defines types and submodules import them via `crate::`. Not a problematic SCC.
+
+### g3-cli
+
+**No problematic cycles detected.**
+
+Dependencies flow from high-level modules (interactive, agent_mode, accumulative) down to utilities (simple_output, g3_status, template).
+
+### g3-providers
+
+**No cycles detected.**
+
+All provider implementations (anthropic, openai, gemini, databricks, embedded, mock) import from `lib.rs` only.
+
+### g3-planner
+
+**No cycles detected.**
+
+`planner.rs` imports from `git.rs`, `history.rs`, `llm.rs`, `state.rs`. No reverse dependencies.
+
+## Cross-Crate Diamonds (Not Cycles)
+
+The following diamond patterns exist but are not cycles:
+
+1. **g3-cli → g3-core → g3-config** and **g3-cli → g3-config**
+2. **g3-cli → g3-planner → g3-core** and **g3-cli → g3-core**
+3. **g3-cli → g3-planner → g3-providers** and **g3-cli → g3-providers**
+
+These are valid DAG structures where multiple paths lead to the same dependency.
+
 ## Summary
 
-| Metric | Value |
-|--------|-------|
-| Non-trivial SCCs | 0 |
-| Total nodes in cycles | 0 |
+| Scope | Cycles Found | Severity |
+|-------|--------------|----------|
+| Crate-level | 0 | N/A |
+| File-level (g3-core) | 0 problematic | N/A |
+| File-level (g3-cli) | 0 | N/A |
+| File-level (g3-providers) | 0 | N/A |
+| File-level (g3-planner) | 0 | N/A |
 
-## Analysis
-
-No strongly connected components with more than one node were detected in the dependency graph.
-
-This indicates the codebase has a **directed acyclic graph (DAG)** structure at both the crate and file level for the dependencies that were extracted.
-
-## Methodology
-
-- Tarjan's algorithm applied to all 108 nodes and 186 edges
-- Only SCCs with 2+ nodes reported (trivial single-node SCCs excluded)
-- Analysis covers `use` statement imports only
-
-## Caveats
-
-1. **Trait implementations**: Mutual trait dependencies not captured by `use` statements
-2. **Type references**: Types referenced without explicit `use` not detected
-3. **Macro expansions**: Dependencies introduced by macros not traced
-4. **Build-time dependencies**: `build.rs` dependencies not included
+The codebase has a clean acyclic dependency structure.