test: add ContextAwareReplacer tests for init/replacers.ts coverage

Add 6 tests for ContextAwareReplacer (lines 392-445) covering:
- returns nothing for < 3-line find patterns
- exact multi-line block match
- trailing newline trimming in find string
- middle-line similarity threshold >= 50% (fuzzy match)
- no match when < 50% similarity (too many differing lines)
- all-empty middle lines always match (totalNonEmptyLines=0 path)

Author: BYK

test/lib/init/replacers.test.ts

@@ -1,5 +1,8 @@
 import { describe, expect, test } from "bun:test";
-import { replace } from "../../../src/lib/init/replacers.js";
+import {
+  ContextAwareReplacer,
+  replace,
+} from "../../../src/lib/init/replacers.js";
 
 describe("replace", () => {
   test("exact match", () => {
@@ -164,3 +167,79 @@ describe("replace", () => {
     });
   });
 });
+
+// ---------------------------------------------------------------------------
+// ContextAwareReplacer
+// ---------------------------------------------------------------------------
+
+describe("ContextAwareReplacer", () => {
+  function* collect(content: string, find: string): Generator<string> {
+    yield* ContextAwareReplacer(content, find);
+  }
+
+  function collectAll(content: string, find: string): string[] {
+    return [...collect(content, find)];
+  }
+
+  test("returns nothing when find has < 3 lines", () => {
+    const content = "line1\nline2\nline3\n";
+    expect(collectAll(content, "line1\nline2")).toEqual([]);
+    expect(collectAll(content, "line1")).toEqual([]);
+  });
+
+  test("finds exact multi-line block", () => {
+    const content = "function foo() {\n  doSomething();\n}\n\nother code\n";
+    const find = "function foo() {\n  doSomething();\n}";
+    const results = collectAll(content, find);
+    expect(results).toHaveLength(1);
+    expect(results[0]).toContain("function foo()");
+    expect(results[0]).toContain("doSomething");
+  });
+
+  test("handles trailing newline in find by trimming it", () => {
+    const content = "start\n  middle line\nend\nother";
+    const find = "start\n  middle line\nend\n"; // trailing newline
+    const results = collectAll(content, find);
+    expect(results).toHaveLength(1);
+  });
+
+  test("matches block where middle lines have >= 50% similarity", () => {
+    // Same first/last line, middle differs slightly
+    const content = "START\n  line a\n  line b\nEND\nextra";
+    const find = "START\n  line a\n  line X\nEND"; // "line X" differs from "line b"
+    // line a matches (1/2 = 50%) → should yield the block
+    const results = collectAll(content, find);
+    expect(results).toHaveLength(1);
+  });
+
+  test("does not match when middle lines have < 50% similarity", () => {
+    // Same first/last, but too many middle lines differ
+    const content = [
+      "START",
+      "  line1",
+      "  line2",
+      "  line3",
+      "  line4",
+      "END",
+    ].join("\n");
+    const find = [
+      "START",
+      "  lineX",
+      "  lineY",
+      "  lineZ",
+      "  lineW",
+      "END",
+    ].join("\n");
+    // 0/4 = 0% match < 50% threshold → no yield
+    const results = collectAll(content, find);
+    expect(results).toHaveLength(0);
+  });
+
+  test("handles block where all middle lines are empty", () => {
+    const content = "OPEN\n\n\nCLOSE\nother";
+    const find = "OPEN\n\n\nCLOSE";
+    const results = collectAll(content, find);
+    // totalNonEmptyLines === 0 → still yields (always match when all empty)
+    expect(results).toHaveLength(1);
+  });
+});