feat(worker): adopt canonical public URL

internal/distworker/runner_test.go

@@ -1149,3 +1149,59 @@ func TestApplyInitStoresURLInMemory(t *testing.T) {
 	assert.Equal(t, "", r.URL(),
 		"URL() must return empty after applyInit with empty URL")
 }
+
+// TestApplyInitPrefersPublicURLOverLegacyURL verifies the bounded-migration
+// precedence on the init/config frame: PublicURL (canonical) wins whenever
+// it is non-empty, and the legacy URL field remains the fallback for old
+// control planes.
+func TestApplyInitPrefersPublicURLOverLegacyURL(t *testing.T) {
+	executor := func(payload interface{}) interface{} {
+		return []wire.CheckResultReport{}
+	}
+	r := newTestRunner(t, 4, 1, executor)
+
+	r.applyInit(&wire.WorkerInit{
+		WorkerID:    "w-1",
+		Concurrency: 2,
+		PublicURL:   "https://canonical.example.com",
+		URL:         "https://legacy.example.com",
+	})
+	assert.Equal(t, "https://canonical.example.com", r.URL(),
+		"PublicURL must win over the legacy URL field")
+
+	r.applyInit(&wire.WorkerInit{
+		WorkerID:    "w-1",
+		Concurrency: 2,
+		URL:         "https://legacy.example.com",
+	})
+	assert.Equal(t, "https://legacy.example.com", r.URL(),
+		"legacy URL field must be used when PublicURL is empty")
+}
+
+// TestApplyInitInvalidAcceptedURLKeepsPrior verifies the safe-fallback
+// behavior when the control plane supplies an unusable advertised URL:
+// the previous accepted value is kept (never regressed to a garbage
+// endpoint), while a valid empty init still clears it.
+func TestApplyInitInvalidAcceptedURLKeepsPrior(t *testing.T) {
+	executor := func(payload interface{}) interface{} {
+		return []wire.CheckResultReport{}
+	}
+	r := newTestRunner(t, 4, 1, executor)
+
+	r.applyInit(&wire.WorkerInit{WorkerID: "w-1", Concurrency: 2, PublicURL: "https://worker.example.com"})
+	assert.Equal(t, "https://worker.example.com", r.URL())
+
+	// Invalid value: keep the previous accepted URL.
+	r.applyInit(&wire.WorkerInit{WorkerID: "w-1", Concurrency: 2, PublicURL: "https://:27401"})
+	assert.Equal(t, "https://worker.example.com", r.URL(),
+		"invalid accepted URL must not replace the stored value")
+
+	r.applyInit(&wire.WorkerInit{WorkerID: "w-1", Concurrency: 2, URL: "not a url"})
+	assert.Equal(t, "https://worker.example.com", r.URL(),
+		"invalid legacy url field must not replace the stored value")
+
+	// Valid empty init clears, as before.
+	r.applyInit(&wire.WorkerInit{WorkerID: "w-1", Concurrency: 2})
+	assert.Equal(t, "", r.URL(),
+		"valid empty init must clear the stored URL")
+}