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/README.md

@@ -0,0 +1,52 @@
+# Vendored agent skills
+
+These skills are vendored copies, not submodules. `link-ai-configs.sh` links every
+directory here into `~/.omo/agent/skills/`, and all of them except
+`frontend-workflow` into `~/.claude/skills/`, so OmO and Claude Code read one
+canonical source instead of divergent copies.
+
+They moved here from `.config/opencode/skills/` when OpenCode was retired; the
+OpenCode-era evaluation notes and rollback steps are in git history at
+`.config/opencode/README.md`.
+
+## Provenance
+
+| Skill | Upstream | Revision | License |
+|---|---|---|---|
+| `impeccable` | [pbakaus/impeccable](https://github.com/pbakaus/impeccable) (`.opencode` integration, skill 4.3.1) | `f2c7051853848826aac2f4646581d62a732155ad` | Apache 2.0, included |
+| `web-design-guidelines` | [vercel-labs/agent-skills](https://github.com/vercel-labs/agent-skills) (`skills/web-design-guidelines/SKILL.md`) | `063bee94c3f4df8453406c830b0a7df0f2860278` | per upstream |
+| ten marketing and copy skills | [coreyhaines31/marketingskills](https://github.com/coreyhaines31/marketingskills) (`skills/`) | `b9ba399dd88b082b926e261e8ccfb843d20aa066` | MIT, copied into each skill |
+| `frontend-workflow` | local | - | - |
+
+The ten marketing skills are `product-marketing`, `copywriting`, `copy-editing`,
+`emails`, `cold-email`, `content-strategy`, `seo-audit`, `ai-seo`, `launch` and
+`social`.
+
+## Local modifications
+
+- **`impeccable`**: every `.opencode/skills/impeccable/scripts/impeccable` command
+  path was rewritten to `~/.omo/agent/skills/impeccable/scripts/impeccable`,
+  including the `allowed-tools` Bash entry and the base-directory fallback in
+  `SKILL.md`. Without this the detector and live-server verbs do not resolve under
+  OmO. `reference/critique.md` also carries an OmO routing line that sends
+  Assessment A to the `design-critique-a` category and Assessment B to
+  `design-critique-b` (defined in `.config/omo/omo.jsonc`).
+- **`web-design-guidelines`**: unchanged. It fetches the current
+  [Web Interface Guidelines](https://raw.githubusercontent.com/vercel-labs/web-interface-guidelines/main/command.md)
+  when invoked, so its rule feed is intentionally not pinned.
+- **marketing skills**: unchanged. They read a per-project
+  `.agents/product-marketing.md` for product context, and a project's own copy
+  skill overrides their generic direct-response advice. Links to the upstream
+  repo's top-level `tools/` directory were not vendored and resolve to nothing.
+
+## Upgrading
+
+Re-copy the same directories from a newer upstream revision, update the revision
+in the table above, then re-apply the local modifications listed for that skill
+and rerun `link-ai-configs.sh`. For `impeccable`, re-apply the path rewrite:
+
+```bash
+cd .config/omo/skills/impeccable
+rg -l -F '.opencode/skills/impeccable/scripts/impeccable' . \
+  | xargs sed -i '' 's#\.opencode/skills/impeccable/scripts/impeccable#~/.omo/agent/skills/impeccable/scripts/impeccable#g'
+```