v0.4.0

Summary

• Prevent stdio MCP servers from killing peer sessions.
• Keep singleton/process coordination confined to future shared-mode startup only.
• Bump the release to 0.4.0 and add regression coverage for stdio coexistence.

Test Plan

• cargo test -p cli-memory-app --test cli_tests serve_stdio_instances_can_coexist_without_killing_each_other -- --nocapture
• cargo test -p cli-memory-app
• cargo build -p cli-memory-app
• npm pack --json