fix(ui): mute completed tool activity

[tt-a1i]

Closes #87

Summary

• render completed compact activity verbs and targets with the theme muted token
• keep pending activity at normal prominence and failures in the error state
• preserve Edit +N / -N accents and Pi-native Ctrl+O expanded rendering
• add a semantic color regression test so later refactors cannot mute active or failed commands accidentally

Validation

• focused renderer tests: 6/6
• bun run check
• full suite: 823 Node tests + 30 Vitest tests, 0 failures
• real Pi TUI smoke from the single local checkout: compact Ran pwd rendered with both verb and target using the configured muted color

Scope

Existing already-open TUI sessions may retain historical component display state. This PR intentionally does not add a historical UI migration; new sessions and newly rendered activity are the supported boundary.