refactor: Remove semantic search and vector embedding functionality

Removes @xenova/transformers dependency, vector storage tables, embedding generation, and semantic search APIs. Simplifies context building to use only FTS search. Eliminates visualizer server, postinstall model download, and related CLI commands. Reduces package size and complexity while maintaining core static analysis capabilities.

src/db/schema.sql

@@ -140,22 +140,6 @@ CREATE INDEX IF NOT EXISTS idx_unresolved_file_path ON unresolved_refs(file_path
 CREATE INDEX IF NOT EXISTS idx_unresolved_from_name ON unresolved_refs(from_node_id, reference_name);
 CREATE INDEX IF NOT EXISTS idx_edges_provenance ON edges(provenance);
 
--- =============================================================================
--- Vector Storage (for future semantic search)
--- =============================================================================
-
--- Vector embeddings for semantic search
--- Note: No foreign key constraint to allow standalone vector testing
--- The VectorManager handles node-vector relationship at the application level
-CREATE TABLE IF NOT EXISTS vectors (
-    node_id TEXT PRIMARY KEY,
-    embedding BLOB NOT NULL, -- Float32 array stored as blob
-    model TEXT NOT NULL, -- Model used to generate embedding
-    created_at INTEGER NOT NULL
-);
-
-CREATE INDEX IF NOT EXISTS idx_vectors_model ON vectors(model);
-
 -- Project metadata for version/provenance tracking
 CREATE TABLE IF NOT EXISTS project_metadata (
     key TEXT PRIMARY KEY,