chore: license AGPL-3.0, zero clippy warnings, CHANGELOG through v1.6.0

License:
- Replace MIT/Apache-2.0 with AGPL-3.0-only across all crates and npm packages
- Replace LICENSE file with official GNU AGPL-3.0 text
- Remove LICENSE-MIT and LICENSE-APACHE

Code quality:
- Fix all 44 clippy warnings (zero remaining)
- Collapsible if statements, redundant closures, manual Option::map
- Remove duplicate #[allow(dead_code)] attributes in deprecated tool modules
- Add Default impl for CognitiveEngine
- Replace manual sort_by with sort_by_key

Documentation:
- Update CHANGELOG with v1.2.0, v1.3.0, v1.5.0, v1.6.0 entries
- Update README with v1.6.0 highlights and accurate stats (52K lines, 1100+ tests)
- Add fastembed-rs/ to .gitignore
- Add fastembed-rs to workspace exclude

1115 tests passing, zero warnings, RUSTFLAGS="-Dwarnings" clean.

crates/vestige-mcp/src/tools/ingest.rs

@@ -140,7 +140,7 @@ pub async fn execute(
 
                 run_post_ingest(cognitive, &node_id, &node_content, &node_type, importance_composite);
 
-                return Ok(serde_json::json!({
+                Ok(serde_json::json!({
                     "success": true,
                     "nodeId": node_id,
                     "decision": result.decision,
@@ -150,7 +150,7 @@ pub async fn execute(
                     "reason": result.reason,
                     "isNovel": is_novel,
                     "embeddingStrategy": embedding_strategy,
-                }));
+                }))
             }
             Err(_) => {
                 let node = storage_guard.ingest(fallback_input).map_err(|e| e.to_string())?;
@@ -162,7 +162,7 @@ pub async fn execute(
 
                 run_post_ingest(cognitive, &node_id, &node_content, &node_type, importance_composite);
 
-                return Ok(serde_json::json!({
+                Ok(serde_json::json!({
                     "success": true,
                     "nodeId": node_id,
                     "decision": "create",
@@ -170,7 +170,7 @@ pub async fn execute(
                     "hasEmbedding": has_embedding,
                     "isNovel": is_novel,
                     "embeddingStrategy": embedding_strategy,
-                }));
+                }))
             }
         }
     }