Reserve prompt orange for slash commands and mentions

[TheGreatAxios]

Summary

• Prompt orange is only for a leading registered slash command and at-mentions
• Skill names and ordinary words in prose stay unstyled
• mcp and plugin attention marks use warning sand, not orange
• Context percent is grey through 60 percent, warning through 80 percent, and error through 100 percent
• Meter is percent-only; warning paint aliases existing SAND

Verification

• bun run typecheck and bun run build pass
• Focused prompt recognition, highlight, chrome, border, and context-window tests pass
• Full bun run test fails one landing assertion when the cwd path contains the substring command; that test scans the whole frame including the bottom-rule cwd. Same test is green on other worktrees. The branch does not change landing.

Fixes CL-6574

[linear-code]

CL-6574

[TheGreatAxios]

Self-review of this branch.

Prompt orange is only a leading registered slash command and at-mentions. Skill names and ordinary words in prose stay unstyled. mcp and plugin attention marks use warning sand, not orange. Context percent is grey through 60, warning through 80, and error through 100. UI.warning aliases existing SAND. The meter is percent-only.

No blocking issues versus the ticket.

Should-fix: the mention matcher has no left boundary, so emails such as foo@bar.com paint as mentions, and trailing punctuation is included.

The landing.test.ts full-suite failure in this worktree is the directory name containing the substring command; that assertion scans the whole frame including the cwd on the bottom rule. The branch does not change landing.