Materialize Jelly's synthesized anonymous-callback signatures as nodes (edges dangle in Neo4j) #13

Follow-up to #11/#12. Jelly emits edges to synthesized anonymous-callback signatures (<host>:<line:col>, from jellyProvider.synthesize()) that are never added to the symbol table, so the endpoints have no node: in analysis.json the edge references a signature absent from symbol_table, and in Neo4j the Cypher writer resolves both ends with MATCH (:Symbol {signature}) and silently drops the relationship when the node is missing. Fix (Option A, mirroring the existing external-symbol mechanism): mint a thin :Symbol:AnonymousCallable {signature,name,path,start_line,start_column,_module} node keyed by signature — jellyProvider returns a synthesized_callables map alongside its edges (built from data it already has at synth time), the union merges it like external_symbols, project.ts emits the nodes plus a DECLARES containment edge from the host symbol/module so they're wipe-reachable, and the catalog/schema.neo4j.json gain the new label. No REL_TYPES change is needed since CALLS/DECLARES already accept Symbol targets by merge-label. Pre-existing in --call-graph-provider jelly; surfaced by #12 making jelly part of the default.