Add streaming to Engine orchestrator (#6094)

# Description of Changes
Adds a streaming endpoint to the Java AI orchestrator
(`/api/v1/ai/orchestrate/stream` in addition to the existing
`/api/v1/ai/orchestrate`). This allows the caller to get updates of what
stage of orchestration is being run at the time so UIs can give the user
feedback.

Also contains some dubious Gradle changes to suppress errors coming from
Spotless, when it crashes in Google stuff. I'm not sure if that's
appropriate to add, feel free to ask for changes in review.

app/common/build.gradle

@@ -7,6 +7,8 @@ spotless {
         target 'src/**/java/**/*.java'
         targetExclude 'src/main/java/org/apache/**'
         googleJavaFormat(googleJavaFormatVersion).aosp().reorderImports(false)
+        // google-java-format 1.28.0 bundles Guava 32.x which crashes Spotless lint on JDK 24/25
+        suppressLintsFor { setStep('google-java-format') }
 
         importOrder("java", "javax", "org", "com", "net", "io", "jakarta", "lombok", "me", "stirling")
         trimTrailingWhitespace()