Document Java memory section and add Copilot Memory links across SDK READMEs

[Morabbin]

Summary

• Add a Java SDK Memory section with working examples for createSession and resumeSession
• Keep Java quick-start flow contiguous by placing Memory after Try it with JBang
• Add an "About GitHub Copilot Memory" link in each SDK Memory section (Node, Python, Go, .NET, Rust, Java)
• Align Java memory examples with runtime requirements by including PermissionHandler.APPROVE_ALL

Testing

• Documentation changes only

[Copilot]

Pull request overview

This PR updates the Java SDK documentation to explain how to configure session “memory” (persistent cross-turn memory) for both new sessions (createSession) and resumed sessions (resumeSession), including how defaults behave under different CopilotClientModes.

Changes:

• Add a new Memory section to java/README.md.
• Document enabling/disabling memory via SessionConfig#setMemory(...) and ResumeSessionConfig#setMemory(...).
• Clarify default behavior when memory is unset for CopilotClientMode.COPILOT_CLI vs CopilotClientMode.EMPTY.

Show a summary per file

File	Description
java/README.md	Adds Memory documentation and examples for configuring memory on create/resume, plus default-mode behavior explanation.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 3

[Copilot]

Copilot's findings

• Files reviewed: 6/6 changed files
• Comments generated: 0 new