feat(server): add boocontext deep analysis tools and synthesis pipeline

- get_symbol_details: type signature, definition location, usage count
- get_call_graph: callers, callees, transitive references
- get_blast_radius added to SYNTHESIS_TOOLS

apps/server/src/services/synthesisPipeline.ts

@@ -35,6 +35,7 @@ export const SYNTHESIS_TOOLS: ReadonlySet<string> = new Set([
   'get_codebase_overview',
   'get_framework_analysis',
   'get_semantic_neighborhoods',
+  'get_blast_radius',
 ]);
 
 const TOP_N_FILES = 5;