fix(javascript): analyze sources containing empty string literals

A single legal empty literal such as `fetch('')`, `require('')`,
`bus.on('', f)`, `localStorage.getItem('')`, or `ipcMain.handle('', f)`
made the whole application analysis fail with `unreadable_output`: the
literal became an application-graph observation label, an artifact-local
identity key, or a semantic node label, all of which must be nonempty.

Normalize display at the two graph construction seams instead of at each
producer: `JavaScriptArtifactGraphAccumulator.addNode` and
`constructSemanticGraphNode` show the empty value as `""` via a shared
`javascriptDisplayText` helper. Observation and node properties keep the
exact empty value. This replaces the per-site `semanticNameLabel` calls.

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

src/application/JavaScriptSemanticGraphValueProjection.ts

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