fix(javascript): keep exact empty env keys and method names

`process.env['']` now projects an exact empty environment key with
complete resolution instead of the same null/partial result as a dynamic
`process.env[key]`. `{ ['']() {} }` keeps its exact empty method name in
the IR instead of a generated `[computed@N]` name.

Semantic graph labels stay nonempty: a shared `semanticNameLabel` helper
displays the empty key as `""` for property slots, config sources, and
function nodes, while `properties.key` keeps the exact value.

Refs #783

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/application/JavaScriptSemanticGraphBuilder.ts

@@ -48,6 +48,7 @@ import {
   addSemanticGraphRelation as addRelation,
   constructSemanticGraphNode as semanticNode,
   createSemanticGraphProjectionState as emptyState,
+  semanticNameLabel,
   type SemanticGraphProjectionState as BuilderState,
 } from "./JavaScriptSemanticGraphConstruction.js";
 
@@ -165,7 +166,8 @@ const projectFile = (
             kind: "function",
             roleKey: `callable:${callable.callableId}`,
             location: callable.location,
-            label: callable.name,
+            label:
+              callable.name === null ? null : semanticNameLabel(callable.name),
             functionNodeId: null,
           },
           state,