Rename project to Tokidachi

[Gaalbu]

Summary

• rename the public project identity, GNOME UUID, extension directory, Java package, Maven artifact, native collector, and Codex client to Tokidachi
• move configuration, cache, backup, package, and release paths to Tokidachi names
• bump the project to 0.3.0 and extension metadata to version 4
• publish a one-time migration guide for users of the former UUID
• remove the completed rename checklist and implementation plan

Compatibility

GNOME treats tokidachi@gaalbu.github.io as a new extension. docs/MIGRATION.md tells existing users how to preserve preferences, disable the old UUID, and install Tokidachi. The old repository URL will redirect after the GitHub rename.

Validation

• mvn clean test
• make test
• mvn package
• java -jar target/tokidachi-0.3.0-all.jar --pretty
• branding contract test covers UUID, metadata, Maven, release artifact, Codex client, and migration guide
• CI builds the native collector and packages both Tokidachi release archives

After this PR merges, the repository will be renamed to Gaalbu/tokidachi and release v0.3.0 will publish the renamed artifacts.