docs: add model scorecard plugin

[zcxGGmu]

Issue for this PR

Closes #35436

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Adds the opencode-model-scorecard community plugin to the ecosystem plugin list. The plugin surfaces model task scores, token prices, and token-efficiency details on the TUI home screen, matching the requested ecosystem docs entry.

This is a fresh small docs-only re-file after #35437 was closed by automated age/reaction cleanup, not for a technical objection.

How did you verify your code works?

• Confirmed the entry was absent from packages/web/src/content/docs/ecosystem.mdx before the change.
• Confirmed bnc4vk/opencode-model-scorecard exists and is not archived.
• bun install --frozen-lockfile to restore the missing local astro binary without changing the lockfile.
• bun run build from packages/web.
• git diff --check.

Note: the pre-push hook runs the repo-wide bun turbo typecheck, which still fails in this Windows checkout on the existing custom-elements.d.ts placeholder issue in app-dependent packages. This docs-only PR does not touch those files; the web build succeeds.

Screenshots / recordings

Not a UI runtime change.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR