Fix weird formatting on augment decorator args (#10556)

Augment decorator args broke asymmetrically (first arg hugging `(`, rest
indented).

## Changes

- **`printAugmentDecoratorArgs`**: Add `softline` before the first
argument (targetType), matching `printCallLikeArgs` behavior for
consistent indentation on break.

## Before/After

```tsp
// Before: first arg hugs paren, closing paren on new line
@@Some.Very.Long.Namespace.Decorator(subscribe1
);

// After: all args indent consistently
@@Some.Very.Long.Namespace.Decorator(
  subscribe1
);

// Before: first arg hugs paren while rest are indented
@@doc(Foo,
  "This is getting very very very long 1",
  "This is getting very very very long 2",
  "This is getting very very very long 3"
);

// After: all args indent consistently
@@doc(
  Foo,
  "This is getting very very very long 1",
  "This is getting very very very long 2",
  "This is getting very very very long 3"
);

// Short lines remain inline
@@doc(Foo, "This is some post doc");
```

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

Author: Copilot

.chronus/changes/fix-formatter-decorator-op-augment-2026-04-29.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/compiler"
+---
+
+Fix formatting of decorators on operations and augment decorators. Decorators on operations now break to separate lines when the total line exceeds the print width. Augment decorator arguments are now consistently indented when the line breaks, matching TypeScript/prettier function call formatting.

.chronus/changes/fix-formatter-decorator-op-augment-java-2026-04-29.md

@@ -0,0 +1,7 @@
+---
+changeKind: internal
+packages:
+  - "@typespec/http-client-java"
+---
+
+Reformat augment decorator arguments in test files to match updated formatter style.

packages/compiler/src/formatter/print/printer.ts

@@ -565,7 +565,7 @@ function printAugmentDecoratorArgs(
     group([
       indent(
         join(", ", [
-          path.call(print, "targetType"),
+          [softline, path.call(print, "targetType")],
           ...path.map((arg) => [softline, print(arg)], "arguments"),
         ]),
       ),

packages/compiler/test/formatter/formatter.test.ts

@@ -2509,10 +2509,24 @@ namespace Foo {
 @@doc(Foo,  "This is getting very very very long 1", "This is getting very very very long 2", "This is getting very very very long 3");
       `,
         expected: `
-@@doc(Foo,
+@@doc(
+  Foo,
   "This is getting very very very long 1",
   "This is getting very very very long 2",
   "This is getting very very very long 3"
+);
+      `,
+      });
+    });
+
+    it("break arguments per lines when decorator name is very long", async () => {
+      await assertFormat({
+        code: `
+@@Some.Very.Long.Namespace.Decorator.Some.Very.Long.Namespace.Decorator.Some.Very.Long.Namespace.Decorator(subscribe1);
+      `,
+        expected: `
+@@Some.Very.Long.Namespace.Decorator.Some.Very.Long.Namespace.Decorator.Some.Very.Long.Namespace.Decorator(
+  subscribe1
 );
       `,
       });

packages/http-client-java/generator/http-client-generator-test/tsp/external.tsp

@@ -52,14 +52,16 @@ interface ExternalOp {
   postExternal(@body body: Body): Body;
 }
 
-@@alternateType(CloudEventDataFormat,
+@@alternateType(
+  CloudEventDataFormat,
   {
     identity: "com.azure.core.models.CloudEventDataFormat",
   },
   "java"
 );
 
-@@alternateType(DayOfWeek,
+@@alternateType(
+  DayOfWeek,
   {
     identity: "java.time.DayOfWeek",
   },