fix(javascript): stop classifying replaced globals as built-in effects

Timer, request, coercion and JSON.parse effects recognized unbound globals
without consulting visible source-local writes, so `setTimeout = f` or
`self.fetch = f` still produced Node timer and fetch operations.

The ambient write owner now classifies a global reference as unmodified,
possibly replaced (a write under an unknown key, such as
`globalThis[k] = v`), or replaced (an exact visible write). Replaced globals
no longer produce built-in effects; possibly replaced ones keep the effect
with partial resolution instead of dropping it. The member-specific
`isUnmodifiedGlobalMember` helper is superseded and removed.

Fixes #3367

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

src/domain/javascript/javascriptSemanticAnalysis.replaced_globals.test.ts

@@ -0,0 +1,57 @@
+import { expect, it } from "vitest";
+
+import { analyzeJavaScriptSemantics } from "./javascriptSemanticAnalysis.js";
+
+const effects = (source: string) => {
+  const ir = analyzeJavaScriptSemantics(source);
+  return {
+    timers: ir.timerOperations.map(
+      ({ method, resolution }) => `${method}:${resolution}`,
+    ),
+    requests: ir.requestOperations
+      .filter(({ kind }) => kind === "request")
+      .map(({ method, resolution }) => `${method}:${resolution}`),
+    parses: ir.boundaryOperations
+      .filter(({ kind }) => kind === "parse")
+      .map(({ method, resolution }) => `${method}:${resolution}`),
+  };
+};
+
+const calls = `
+  function work() {}
+  setTimeout(work, 100);
+  fetch("https://example.invalid");
+  JSON.parse("null");
+`;
+
+it("does not classify calls to replaced globals as built-in effects", () => {
+  expect(
+    effects(`
+      setTimeout = () => null;
+      fetch = () => null;
+      JSON.parse = () => null;
+      ${calls}
+    `),
+  ).toEqual({ timers: [], requests: [], parses: ["parse:partial"] });
+});
+
+it("keeps built-in effects partial after a write under an unknown key", () => {
+  expect(
+    effects(`
+      globalThis[Symbol.for("registry")] = new Map();
+      ${calls}
+    `),
+  ).toEqual({
+    timers: ["setTimeout:partial"],
+    requests: ["fetch:partial"],
+    parses: ["JSON.parse:partial"],
+  });
+});
+
+it("keeps built-in effects for unmodified globals", () => {
+  expect(effects(calls)).toEqual({
+    timers: ["setTimeout:complete"],
+    requests: ["fetch:complete"],
+    parses: ["JSON.parse:complete"],
+  });
+});