fix: normalize "bedrock" provider ID to "amazon-bedrock"

Add "bedrock" and "aws-bedrock" as aliases for the canonical
"amazon-bedrock" provider ID in normalizeProviderId().

Without this mapping, configuring a model as "bedrock/..." causes
the auth resolution fallback to miss the Bedrock-specific AWS SDK
path, since the fallback check requires normalized === "amazon-bedrock".
This primarily affects the main agent when the explicit auth override
is not preserved through config merging.

Fixes #15716

src/agents/model-auth.test.ts

@@ -77,6 +77,18 @@ describe("resolveModelAuthMode", () => {
       ),
     ).toBe("aws-sdk");
   });
+
+  it("returns aws-sdk for bedrock alias without explicit auth override", () => {
+    expect(resolveModelAuthMode("bedrock", undefined, { version: 1, profiles: {} })).toBe(
+      "aws-sdk",
+    );
+  });
+
+  it("returns aws-sdk for aws-bedrock alias without explicit auth override", () => {
+    expect(resolveModelAuthMode("aws-bedrock", undefined, { version: 1, profiles: {} })).toBe(
+      "aws-sdk",
+    );
+  });
 });
 
 describe("requireApiKey", () => {

src/agents/model-selection.test.ts

@@ -19,6 +19,9 @@ describe("model-selection", () => {
       expect(normalizeProviderId("OpenCode-Zen")).toBe("opencode");
       expect(normalizeProviderId("qwen")).toBe("qwen-portal");
       expect(normalizeProviderId("kimi-code")).toBe("kimi-coding");
+      expect(normalizeProviderId("bedrock")).toBe("amazon-bedrock");
+      expect(normalizeProviderId("aws-bedrock")).toBe("amazon-bedrock");
+      expect(normalizeProviderId("amazon-bedrock")).toBe("amazon-bedrock");
     });
   });
 

src/agents/model-selection.ts

@@ -50,6 +50,9 @@ export function normalizeProviderId(provider: string): string {
   if (normalized === "kimi-code") {
     return "kimi-coding";
   }
+  if (normalized === "bedrock" || normalized === "aws-bedrock") {
+    return "amazon-bedrock";
+  }
   // Backward compatibility for older provider naming.
   if (normalized === "bytedance" || normalized === "doubao") {
     return "volcengine";