fix(tui): refresh terminal interface design (#267)

## Related Issue

Resolve #266

## Problem

See linked issue.

## What changed

- Reworked the dark and light semantic palettes with cyan actions, coral
accents, stronger neutral text, and accessible active-tab colors.
- Clarified transcript hierarchy, reduced successful-tool visual weight,
and aligned welcome and footer styling.
- Made active Dynamic Workflow progress cyan and retained green for
completed progress.
- Preserved the Pythinker logo bot and existing interaction behavior.
- Updated theme documentation and added a patch changeset.

## Verification

- `pnpm --dir apps/pythinker-code exec vitest run test/tui` — 146 files
and 2,098 tests passed.
- `pnpm --dir apps/pythinker-code exec tsc -p tsconfig.json --noEmit`
- `pnpm exec tsgo -p apps/pythinker-code/tsconfig.json --noEmit`
- `pnpm lint` — 0 errors.
- `pnpm --dir docs run build`
- `git diff --check`
- GitNexus compare risk: LOW, with zero affected execution processes.

## Checklist

- [x] I have read the
[CONTRIBUTING](https://github.com/PyModel/pythinker-code/blob/main/CONTRIBUTING.md)
document.
- [x] I have linked a related issue.
- [x] I have added tests that prove the feature works.
- [x] Ran `gen-changesets` skill and added the approved patch changeset.
- [x] Ran `gen-docs` skill and verified the updated theme documentation.


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Improvements**
* Refined terminal colors for stronger contrast and clearer visual
hierarchy.
* Updated tabs, dialogs, messages, headings, status indicators, and
model labels with consistent styling.
* Improved narrow-terminal footer layout to prioritize essential status
information.
  * Clarified permission, plan, mode, and workflow progress states.
* Successful tool results now use an unfilled appearance; pending and
failed states remain highlighted.

* **Documentation**
  * Updated theme customization guidance and color-token descriptions.

* **Tests**
* Expanded coverage for accessibility contrast, responsive layouts,
themes, messages, tools, tabs, and workflow progress.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: elkaix