chore: rename context-graph to rippletide-code

[johan-rippletide]

Summary

• rename context-graph to rippletide-code so the directory matches the published CLI
• update the release workflow, version-bump script, ignore paths, and README
• keep npm package names, CLI commands, backend endpoints, and packaged contents unchanged

Validation

• version-bump script smoke-tested against an isolated repository copy
• npm manifests parsed successfully
• npm launcher passed node syntax validation
• Rust include_str resources and release workflow paths verified
• no tracked context-graph path references remain
• git diff --check passed

Release impact

No npm re-release is required because this changes only the repository layout.