ai-usagebar in Anchor Shell

The upstream/ directory vendors the Rust application from akitaonrails/ai-usagebar, version 1.30.0, commit ad28ba6118b6ac391ea54b76a0498c76d814de22 (MIT license). The upstream Markdown documentation, referenced screenshots, and LICENSE are kept beside the vendored source at that same revision. This keeps the upstream documentation links in the README working offline and makes the license and update history reviewable with the source.

The package derivation in ../ai-usagebar.nix builds its CLI and TUI from this copy, so updates and local changes are reviewed with this system repository. When updating, refresh the source and its documentation together, then update the pinned revision above.

The Anchor Shell adaptation lives in ../../anchor-shell/plugins/ai-usagebar/. It reads the selected provider's JSON report, refreshes every five minutes, and shows its custom Quickshell usage panel on click. The bar does not launch the upstream terminal TUI. The HX90 package and the default bar layout are wired in the host and shell configuration. See that plugin's README for the shell integration and its differences from upstream.