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/JavaScriptSemanticGraphDataProjection.ts

@@ -10,6 +10,7 @@ import {
   addSemanticGraphRelation,
   addSemanticGraphUnknown,
   constructSemanticGraphNode,
+  semanticNameLabel,
 } from "./JavaScriptSemanticGraphConstruction.js";
 import { unknownSemanticEvidence } from "./JavaScriptSemanticGraphEvidence.js";
 import {
@@ -78,7 +79,10 @@ const addConfigurationNode = (
         kind: "config-source",
         roleKey: operation.configId,
         location: operation.location,
-        label: operation.key ?? operation.kind,
+        label:
+          operation.key === null
+            ? operation.kind
+            : semanticNameLabel(operation.key),
         functionNodeId:
           operation.ownerCallableId === null
             ? null