chore(tokens): migrate hardcoded hex colors to design tokens

[juancarlosbs]

Resolves the tech debt deferred from PR #15 (CodeRabbit finding on docs/ui.md): three components carried hardcoded hex colors in violation of the token-only styling convention.

Spec: docs/superpowers/specs/2026-07-27-hex-to-tokens-design.md · Plan: docs/superpowers/plans/2026-07-27-hex-to-tokens.md

• Four new tokens in src/App.css (@theme): --color-env-development/staging/production/neutral, keeping the exact traffic-light values the dots already use.
• New envDotClass() helper in src/lib/envColor.ts replaces the environment-color map that was duplicated in EnvSelector and SettingsDialog; dots now use bg-env-* classes instead of inline styles.
• EnvSelector, SettingsDialog, and WorkspaceSwitcher migrated to existing surface tokens (bg-card, bg-secondary, border-border, bg-sidebar-accent) — all value-identical swaps.
• Only visual change: the SettingsDialog sidebar background #141414 → bg-sidebar (#18181b), an imperceptible shift approved in the spec to avoid a single-use token.
• Docs: --env-* family added to docs/stack.md and docs/ui.md.

Verification: hex sweep over src/ (excluding App.css/assets) returns empty · pnpm test 111 passed · tsc --noEmit clean · vite build output confirmed to contain the generated bg-env-* utilities. Built task-by-task with per-task review plus a final whole-branch review (clean).

🤖 Generated with Claude Code

https://claude.ai/code/session_013r5tZbG4bjfbK1aqj1SyzQ