feat(omo): retire opencode and move its skills and commands to omo

- Move the vendored skills from .config/opencode/skills to
  .config/omo/skills, with provenance and local changes in its README
- Rewrite Impeccable's script paths to ~/.omo/agent/skills/impeccable so
  its detector and live-server verbs resolve under omo
- frontend-workflow hands screenshots to a visual-engineering task
  instead of opencode run
- Move the notes commands and /impeccable to .config/omo/prompts as omo
  prompt templates; setup-mcp stays behind because it writes
  opencode.json
- Archive DEVELOPMENT-WORKFLOW.md and UI-WORKFLOW.md under
  .config/omo/archive; nothing loads them
- link-ai-configs.sh links the skills into omo and Claude Code only and
  stops linking OpenCode's config, TUI, plugins and workflow docs
- setup-mac.sh and Brewfile.apps stop installing OpenCode; README and
  .withcontextconfig.jsonc follow the new layout

~/.config/opencode/AGENTS.md stays linked: omo's rules engine reads it
before ~/.claude/CLAUDE.md and stops at the first hit, so it carries the
shared preferences and keeps OMC's instructions out of omo.

.config/omo/skills/frontend-workflow/references/dotfiles-workbench.md

@@ -0,0 +1,13 @@
+# Dotfiles workbench: project-specific context
+
+Evidence: the repository README describes macOS developer tooling, productivity, aesthetics, and developer experience. Existing configuration is primarily terminal/editor tooling, not a committed web design system.
+
+Audience: developer checking a workstation configuration. Primary action for the evaluation fixture: run a safe simulated readiness check and understand any failure. All fixture data must be labelled demo data; never imply it is a real system inspection.
+
+Approved visual references: none supplied or found for this new web surface. Impeccable and Vercel are process references, not approval to imitate their sites. Any user-supplied project reference supersedes these proposals.
+
+Proposed defaults for the fixture only: calm, precise, task-focused light interface; system-ui body text, monospace for technical values; 16px body with 1.5 line-height and 14px minimum secondary text; canvas #f5f7fb, surface #fff, ink #172234, secondary #475569, action #1d4ed8. Verify rendered contrast rather than assuming tokens guarantee it.
+
+Proposed spacing: 4/8/12/16/24/32/48px, content near 1040px maximum, 16-24px mobile gutters. Components: labelled filter/scenario controls, one dominant Run checks action, readable check rows, explicit result/empty/error feedback. Use no decorative imagery unless it explains the task. Preserve focus, disabled/loading feedback and reduced motion.
+
+Do not apply these defaults to other applications. Read their design system and audience first.