docs: separate Jenkins trigger onto jenkins-write-mcp boundary (#152)

Document that build triggers live on the gated jenkins-write-mcp server,
not the read-only jenkins-mcp surface. Add registration and safety-model
cross-links plus doc tests that fail if trigger tools reappear on the read
boundary.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

docs/architecture/jenkins-readonly-build-status-design.md

@@ -5,7 +5,7 @@
 - **Related:** #77 (repo/branch/PR → job mapping, designed separately)
 - **Date:** 2026-07-02
 
-Note on naming: This design used historical `jenkins-readonly` skill name in Gitea-Tools. Actual package/server is `jenkins-mcp` (see mcp-control-plane registration in #55). The server boundary now contains gated trigger (see #56), but read tools remain as designed.
+Note on naming: This design used historical `jenkins-readonly` skill name in Gitea-Tools. Actual package/server is `jenkins-mcp` (see mcp-control-plane registration in #55). The read server boundary remains read-only; gated triggers live on the separate `jenkins-write-mcp` / `jenkins_mcp.write_server` boundary (see #56 / #152).
 Client registration and reload instructions live in
 [`../mcp-client-registration.md`](../mcp-client-registration.md).
 
@@ -18,7 +18,9 @@ detail (build URL, number, timing, result) to report or investigate.
 Phase 1 is **primarily read-only**, per ADR-0001
 ([`adr-0001-mcp-control-plane-boundaries.md`](adr-0001-mcp-control-plane-boundaries.md)):
 
-- Build triggers are gated behind dedicated profile + exact confirmation (landed in #4, boundary correction in #56).
+- Build triggers are outside this read-only surface and require the separate
+  `jenkins-write-mcp` boundary, a dedicated profile, exact confirmation, and
+  fail-closed mutation audit (landed in #4, boundary correction in #56 / #152).
 - **Excluded: deploy triggers.**
 - **Excluded: parameterized job launches.**
 - Excluded: job creation/deletion/config changes, queue manipulation, node
@@ -109,7 +111,7 @@ by #76):
   `forbidden_operations: ["jenkins.build.trigger", "jenkins.deploy", "jenkins.job.configure"]`
   as belt-and-braces even though no mutating tool exists.
 - Missing URL/user/token/profile ⇒ **fail closed** with a clear message.
-- Since every tool is read-only, no confirmation gates are needed — but
+- Since every tool on `jenkins-mcp` is read-only, no confirmation gates are needed — but
   identity (`jenkins_whoami`) must still work so workflows can prove which
   Jenkins account they act as.