feat: add /add-portal command for generating local job-portal search skills (#37)

The README has always invited users outside Denmark to build equivalents of
the four Danish portal CLI skills, but doing so meant reverse-engineering
.agents/skills/*/cli/ by hand. /add-portal turns that invitation into a
guided workflow:

- Interviews the user for the portal URL, skill name, market/language
  (trigger phrases in the local language, like the Danish skills), and a
  realistic test query
- Investigates the portal before writing code: search-URL pattern, result
  structure (JSON API preferred over HTML), detail-page pattern, robots.txt
  and access rules. Auth-walled portals are declined; portals with
  restrictive terms get a prominent personal-use-only warning in the
  generated SKILL.md (same as linkedin-search)
- Scaffolds from the canonical structure with linkedin-search as the
  zero-dependency reference, enforcing the shared portal-skill contract:
  search/detail commands, common flags, {meta, results} JSON shape, stderr
  JSON errors, backoff on 429/5xx, chunked parsing
- Mandatory live test-run (search + detail + test suite) before registering
- Optionally wires the portal into /scrape via search-queries.md

The generator is country-agnostic; its output is market-specific and stays
in the user's fork, matching the repo policy that upstream remains a
universal template.

Docs: README (commands list, file structure, Job search tools section) and
SETUP.md (CLI install section pointer).

SETUP.md

@@ -59,6 +59,8 @@ done
 
 For `linkedin-search` the install is optional: it has zero runtime dependencies and runs with plain `bun`; `bun install` only pulls TypeScript dev types.
 
+If you're outside Denmark, you can generate an equivalent search skill for your local job board with `/add-portal` — it scaffolds the same CLI structure for any public portal and test-runs a live query before registering. See the "Job search tools" section in the README.
+
 ## 4. Run the setup interview
 
 Start Claude Code in the repository: