docs(skills): restore and rewrite opencli-usage as orientation skill

[jackwener]

Summary

• Restore skills/opencli-usage/SKILL.md, deleted in refactor: consolidate 6 skills into 3, remove mechanical commands #1094. Its role — top-level orientation to what opencli is, how to discover adapters, what flags/env/formats are universal, and which specialized skill to load next — was not covered by any of the 3 post-consolidation skills. Per @WAWQAQ's follow-up to docs(skills): restore and upgrade opencli-browser skill #1119, this was an unintended removal.
• Deliberately not a verbatim restore of the old 247-line file (+910-line commands.md +105 desktop.md +82 plugins.md). The old version hand-maintained a 100-adapter command table; it rotted fast and PR refactor: consolidate 6 skills into 3, remove mechanical commands #1094 cited that as the reason for removal. The new version:
  • Points agents at opencli list -f json as the source of truth, instead of hardcoding a table.
  • Keeps the meta-structure agents actually need: three pillars (adapters / browser driving / external-CLI passthrough), the strategy tags (PUBLIC | COOKIE | HEADER | INTERCEPT | UI | LOCAL) and what each implies for prerequisites, universal flags (-f, -v), output formats, env vars, self-repair hook, adapter authoring paths, plugins, external CLI passthrough.
  • Explicitly lists commands the refactor: consolidate 6 skills into 3, remove mechanical commands #1094 consolidation removed (explore, record, web / desktop top-level groups) so agents don't try to invoke them.
  • Cross-links to the post-consolidation skills: opencli-browser, opencli-adapter-author, opencli-autofix, smart-search.
• Update opencli-adapter-author description to stop claiming it replaces opencli-usage.

167 lines vs. the old 247 — smaller, and every claim is cross-checked against src/cli.ts, src/external.ts, src/output.ts, src/electron-apps.ts, src/doctor.ts, src/discovery.ts. Sibling PR for reference: #1119 (opencli-browser restore).

Test plan

• Frontmatter parses (name / description / allowed-tools).
• Every claim cross-referenced against today's source (meta commands, universal flags, output formats, env vars, strategy enum, adapter discovery paths, electron app list, external-CLI passthrough flow).
• Removed-command list matches the refactor: consolidate 6 skills into 3, remove mechanical commands #1094 delta.
• opencli-adapter-author description aligned.
• Reviewer sanity-check: no fabricated flags, no stale env vars, cross-links correct.