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/JavaScriptSemanticGraphValueProjection.ts

@@ -7,6 +7,7 @@ import {
   addSemanticGraphNode,
   addSemanticGraphRelation,
   constructSemanticGraphNode,
+  semanticNameLabel,
 } from "./JavaScriptSemanticGraphConstruction.js";
 import type { SemanticFlowProjectionContext } from "./JavaScriptSemanticGraphFlowProjection.js";
 
@@ -116,7 +117,7 @@ export const semanticPropertySlot = (
         kind: "property-slot",
         roleKey: `property:${objectBindingId}:${name}`,
         location: null,
-        label: name === "" ? '""' : name,
+        label: semanticNameLabel(name),
         functionNodeId:
           context.bindingNodes.get(objectBindingId)?.function_node_id ?? null,
         properties: {