fix: refine earth hud structure and bun startup flow

- refactor the /earth HUD into class-first CSS layers with dedicated base, hud, and toolbar responsibilities
- clean up Earth markup and runtime DOM hooks so shared panel, toolbar, tooltip, and status classes stay consistent after dynamic updates
- keep HUD scaling configurable through extracted constants and remove leftover legacy panel/toolbar styling paths
- make planet.sh self-bootstrap Bun and uv by prepending local runtime bins to PATH and auto-installing missing tools in fresh environments
- document Bun as the frontend package manager of record and sync repository version metadata to 0.24.1

rules.md

@@ -157,6 +157,9 @@ git fetch origin && git rebase origin/main
 - Prefer well-maintained, widely-used libraries
 - Pin dependency versions in `pyproject.toml`, `uv.lock`, and `package.json`
 - Review security advisories with `pip-audit` and `bun audit`
+- Frontend package management and script execution use **Bun only**
+- Frontend commands must use `bun install` / `bun run ...`
+- **NEVER** use `npm` / `pnpm` / `yarn` for the frontend project
 - **NEVER** add unknown packages
 
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