docs(kernel): list services.sms in the runtime-services stability matrix, and gate the matrix and its labels (#9684)

`versioning.mdx`'s "Current Matrix" carried seven rows for the chapter's eight
pages: `services.sms` was missing from a FIFTH enumeration of the same chapter,
after #9604 fixed it in two index lists and #9630 fixed the accessor/slot
mismatch. Every enumeration of this chapter that the gate does not hold has
drifted, and each one was found by a human noticing.

So the row is the small half. `check-runtime-services-index.mjs` gains two
additive limbs, leaving the five existing checks untouched:

- check 6 holds the "Current Matrix" to the pages on disk — membership and
  order, exactly as check 3 holds the chapter list, because the matrix follows
  meta.json's nav order and that convention is the only thing that tells the
  next author where a new row goes;
- check 7 holds every published stability LABEL to the page's own
  `- **Stability:** <label>` bullet, on BOTH tables that publish one — the
  matrix and the `services.*` table in `kernel/index.mdx`. This is the half
  with lasting value: membership checking catches a MISSING row, this catches a
  WRONG one, which is a live lie a reader plans an upgrade against.

The page is the source of truth for its own label, so a disagreement is always
reported against the table, and a page that declares no label at all is a
finding.

The `services.sms` label is derived, not invented: `sms-service.mdx` declares
`- **Stability:** `stable``, which is what the row now says.

#9629 is untouched: the stability row parser is anchored to `^|` table rows, so
the Source-of-Truth list's prose `Security:` row — the one #9634 deliberately
kept out of the gate — cannot enter any set here. The self-test pins that on
the parser and again on a failing tree.

Self-test 17 -> 27 assertions.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XqDQYVU5smx29ts9pAErja

Author: claude

.github/workflows/lint.yml

@@ -530,6 +530,14 @@ jobs:
       # order) to them. It lives in this job with the other docs guards: the edit
       # that breaks it is a docs edit, so a packages/** paths filter would blind
       # it to its own failure mode.
+      #
+      # #9630 added a fourth claim: each page names the registry slot
+      # ctx.getService() really resolves it by. #9684 added a FIFTH enumeration
+      # of the same chapter -- versioning.mdx's "Current Matrix" shipped seven
+      # rows for eight pages -- so the gate now holds that matrix to the pages
+      # too, and holds every stability LABEL it and the kernel/index.mdx table
+      # publish to the page's own Stability bullet. That second half catches a
+      # WRONG row, which membership checking passes silently.
       - name: Runtime-services indexes enumerate the chapter's real pages
         run: pnpm check:runtime-services-index
 

content/docs/kernel/runtime-services/versioning.mdx

@@ -27,5 +27,6 @@ When a runtime service API changes in a breaking way:
 | `services.audit` | `experimental` |
 | `services.queue` | `stable` |
 | `services.email` | `stable` |
+| `services.sms` | `stable` |
 | `services.settings` | `stable` |
 | `services.storage` | `stable` |