#215 fix: use current OpenCode theme tokens

Summary

• Update @opencode/plugin to 2.1.3, matching the running OpenCode version.
• Read the current theme tokens in force-input and usage-limits; keep support for older token shapes.
• Add regression coverage for the new token names.

Testing

• Force-input and usage-limits tests, typechecks, builds, and package smoke tests pass.
• Root formatting and typechecks pass.

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Summary by cubic

Updates opencode-force-input and opencode-usage-limits to read the current OpenCode 2.1.3 theme tokens (base, muted) instead of the old ones (default, subdued), so colors render correctly on the running OpenCode version.

• Bumps @opencode/plugin to 2.1.3 to match.
• Keeps fallback support for the older token shapes and the legacy flat theme.
• Adds regression tests covering the new, previous, and legacy token shapes, plus per-threshold usage status colors.