N+1 dry-run: examplehost (stub)

Phase 111.6.2 — do not implement a real ExampleHost. This page proves the admission path fits in one PR without new case-statement snowflakes.

Checklist (complete without shipping code)

1. [ ] Native intercept? → if no, safety_model: none, max tier packaging/candidate
2. [ ] Deny fail-open/closed documented
3. [ ] Event coverage table (shell/file/MCP)
4. [ ] scripts/setup-examplehost.sh with --check + isolated HOME
5. [ ] Static smoke test path registered
6. [ ] HARNESS_EXAMPLEHOST_*_SMOKE_REQUIRED documented
7. [ ] Bootstrap route named in bootstrap-routing-contract
8. [ ] support-claim wording patterns added
9. [ ] docs/research/examplehost-adapter-candidate.md
10. [ ] floor_member true only after live deny
11. [ ] Allowed/blocked public phrases
12. [ ] Capability matrix row

Registry row (illustrative only)

{
  "id": "examplehost",
  "display_name": "ExampleHost",
  "tier": "future/unsupported",
  "setup_script": "scripts/setup-examplehost.sh",
  "dist_host": "examplehost",
  "routing_host": "examplehost",
  "safety_model": "none",
  "floor_member": false,
  "smoke": {
    "static": ["tests/test-examplehost-adapter.sh"],
    "setup_check": "scripts/setup-examplehost.sh --check",
    "adapter": "tests/test-examplehost-adapter.sh"
  },
  "blocked_public_phrases": ["supported ExampleHost", "正式対応.*ExampleHost"]
}

What must NOT grow

• New hard-coded case "$HOST" in ... examplehost) blocks in release-preflight (use hosts/registry.json smoke loop instead)
• Duplicate skill trees under skills-examplehost/

Verification of dry-run (this PR)

test -f docs/onboarding/host-admission.md
test -f hosts/registry.json
bash tests/test-host-registry.sh

Adding a real host is: copy this stub → fill checklist → append registry row → add setup/smoke scripts → update public tier tables once evidence exists.