Add chalice theme

[huangkairan]

Adds Chalice, a minimalistic dark/light color theme port of Artem Laman's Chalice for VSCode (MIT-licensed) to Zed.

What's in this PR

• New submodule extensions/chalice pinned to v0.1.0 (huangkairan/chalice-theme-zed)
• New entry in extensions.toml

Variants

• Chalice Dark — low-contrast teal / green / violet on near-black
• Chalice Light — earthy browns / blues on warm off-white

Chalice highlights only strings, numbers, comments, and global definitions; everything else uses the editor foreground (no italics, no bold). The goal is to reduce visual noise.

Checks

• Repository contains an MIT LICENSE file
• pnpm sort-extensions run
• pnpm test passes locally (111/111)
• Local validation script passes for both theme JSON files
• Source repo tagged v0.1.0

[cla-bot]

We require contributors to sign our Contributor License Agreement, and we don't have @huangkairan on file. You can sign our CLA at https://zed.dev/cla. Once you've signed, post a comment here that says '@cla-bot check'.

[huangkairan]

@cla-bot check

[cla-bot]

The cla-bot has been summoned, and re-checked this pull request!

[huangkairan]

@maxdeviant