fix(javascript)!: stop copying literals into semantic metadata (#1407)

Commit literal values with canonical JSON SHA-256 in semantic role keys
and use a type label for strings. Preserve complete values, provenance and
literal queries while avoiding two payload copies in each string node.

Verify real compiled CLI/default stdio MCP, typed union seeds, empty
strings and trace continuation with a large source-owned fixture.

Refs #723

BREAKING CHANGE: Newly produced semantic literal node IDs use
value-sha256 role keys, and string labels read "string literal". Read exact
values from properties.value and obtain node IDs from the selected parent
graph. Previously stored Evidence and its original IDs remain valid.

src/application/javascript/JavaScriptSemanticGraphValueProjection.ts

@@ -2,6 +2,7 @@ import {
   semanticContainer,
   semanticPropertyPointer,
 } from "../../domain/javascript/javascriptSemanticSlots.js";
+import { digestCanonicalValue } from "../../domain/canonicalDigest.js";
 import type { JavaScriptSemanticBinding } from "../../domain/javascript/javascriptSemanticIr.js";
 import type {
   JavaScriptSemanticProperty,
@@ -156,9 +157,11 @@ const addLiteralNode = (
 ) =>
   retainSemanticGraphNode(context.state, context.file, {
     kind: "literal",
-    roleKey: `literal:${binding.bindingId}:${role}:${JSON.stringify(value)}`,
+    // Identity needs an exact value commitment, not another payload copy.
+    // Keep the complete literal in properties for queries and Evidence export.
+    roleKey: `literal:${binding.bindingId}:${role}:value-sha256:${digestCanonicalValue(value, "Semantic literal")}`,
     location: binding.definitions[0]?.location ?? null,
-    label: JSON.stringify(value),
+    label: typeof value === "string" ? "string literal" : JSON.stringify(value),
     functionNodeId:
       context.bindingNodes.get(binding.bindingId)?.function_node_id ?? null,
     properties: { value },