feat(modules): the three de-entanglement registries, with core as the registrant

Phase 2 PR 4 of docs/website/MODULE_SYSTEM.md §2.7. Adds server/src/modules/registries.js
and moves core's own notification streams, announce leg and users-detail routes
behind it, so the three seams §1.8 and §1.9 named are exercised on every boot
before any module depends on them.

Registering is validate-then-commit per registrant: the loader stages what a
module claims and the second pass commits it, so a module that throws halfway
through register() — or fails checkDeclared after it — leaves nothing behind.
That is the registry-side twin of PR 2's second-pass mount rule.

Four decisions, all the recommended option:

- announce legs became a child table. `announce_job_legs` replaces the
  towncrier_*/discord_* column groups, so the leg set is data: core registers
  `discord`, module-uo will register `towncrier`, and a module cannot ALTER a
  core table to add its own. Backfill is guarded on information_schema (a
  SELECT of a dropped column is a parse error, not a runtime one) and the
  columns go with DROP COLUMN IF EXISTS. Verified against the live dev DB:
  three legacy jobs migrated faithfully, three replays, no duplicates.
- `mapEvent` dropped from registerNotificationStreams. §1.8 already inverts the
  push path so a module owns fromShardEvent and calls core's publish() with a
  stream id it resolved; a second mapping mechanism was a leftover. The public
  safety filter, the kinds it reads and the streams it protects now live in one
  file and move together.
- core registers through the same staging area a module uses, via an explicit
  registries.registerCore() in app.js before modules.load().
- core's six /admin/users/:id/shard/* paths now go through the
  `admin.users.detail` slot, and getUser moved back to admin.controller.js.

Found on the way, and the reason two build tools changed:

- scripts/routeManifest.js could not decode a parameterised mount. Its
  unwinder expected `(?:([^\/]+?))`; express 4.22 emits `(?:\/([^/]+?))` with
  the separator inside the group. The branch had never run. It threw rather
  than guessing, which is what it is for.
- swagger-autogen cannot follow a route into an extension slot — the slot's
  router is created by declareSlot() and filled later, so there is no literal
  mount for a static parse. Regenerating deleted 407 lines and printed
  `Swagger-autogen: Success`, the spike's exact failure (MODULE_API.md §7.4).
  swagger/slotSpecs.js generates a fragment per filled slot and re-roots it at
  the prefix the router actually hangs at in the live app — read from the
  express stack via routeManifest's own mountPath, so the manifest and the spec
  cannot disagree. swagger/mergeSpec.js is the merge helper core owes for
  module fragments anyway (§6.1a), proved here against core's own slot first.

884 tests pass (856 before). routes.manifest.json is unchanged at 229 routes.
The OpenAPI spec diff is two lines of intent: the retry endpoint's summary, and
its `leg` no longer being a fixed enum.

Co-Authored-By: Claude <noreply@anthropic.com>

server/src/model/announceJobs/announceJobs.model.js

@@ -2,19 +2,21 @@
 //
 // Sits between the DB rows and the worker: creates jobs on publish, records each
 // leg's outcome, keeps the parent `status` rollup in sync, stamps the post's
-// announced_at when both legs land, and resets a leg for the admin retry button.
-// The pure decisions (backoff, rollup, classification) live in .logic.js.
+// announced_at when every leg lands, and resets a leg for the admin retry button.
+// The pure decisions (backoff, rollup) live in .logic.js; which legs exist at all
+// is modules/registries.js's answer, not this file's (MODULE_SYSTEM.md §1.8).
 
 const db = require('./announceJobs.db')
 const logic = require('./announceJobs.logic')
+const registries = require('../../modules/registries')
 const posts = require('../posts/posts.model')
 const log = require('../../utils/logger')('announce')
 
-// Enqueue an announcement for a freshly-published news post: one job row (both
-// legs pending, due immediately) plus a back-pointer on the post so the admin
-// panel can find it. Returns the new job id.
+// Enqueue an announcement for a freshly-published news post: one job row, one leg
+// row per registered leg (all pending, due immediately), plus a back-pointer on
+// the post so the admin panel can find it. Returns the new job id.
 async function enqueue(postId) {
-  const jobId = await db.create(postId)
+  const jobId = await db.create(postId, registries.announceLegIds())
   await posts.linkAnnounceJob(postId, jobId)
   log.info('announce job enqueued', { jobId, postId })
   return jobId
@@ -43,12 +45,13 @@ async function enqueueIfNeeded(post, transition) {
   }
 }
 
-// Record a leg's dispatch outcome and refresh the rollup. `outcome` is one of
-// logic.classify*'s results: 'done' | 'retry' | 'terminal'. For 'retry' we bump
-// the attempt count and schedule the next run (or fail the leg once the cap is
-// hit). Returns the updated job row.
+// Record a leg's dispatch outcome and refresh the rollup. `outcome` is one of a
+// leg's classify() results: 'done' | 'retry' | 'terminal'. For 'retry' we bump the
+// attempt count and schedule the next run (or fail the leg once the cap is hit).
+// Returns the updated job row.
 async function recordOutcome(job, leg, { outcome, error }) {
-  const attempts = Number(job[`${leg}_attempts`]) || 0
+  const row = (job.legs || []).find((l) => l.leg === leg)
+  const attempts = Number(row && row.attempts) || 0
 
   if (outcome === 'done') {
     await db.updateLeg(job.id, leg, { status: 'done', attempts, lastError: null, nextAttemptAt: null })
@@ -71,12 +74,12 @@ async function recordOutcome(job, leg, { outcome, error }) {
   return refreshStatus(job.id)
 }
 
-// Recompute and persist the parent status from the two legs; stamp the post's
-// announced_at the moment both legs have delivered.
+// Recompute and persist the parent status from the legs; stamp the post's
+// announced_at the moment every leg has delivered.
 async function refreshStatus(jobId) {
   const job = await db.findById(jobId)
   if (!job) return null
-  const status = logic.rollupStatus(job.towncrier_status, job.discord_status)
+  const status = logic.rollupStatus(job.legs.map((l) => l.status))
   if (status !== job.status) await db.setStatus(jobId, status)
   job.status = status
   if (status === 'done') {
@@ -93,16 +96,33 @@ async function refreshStatus(jobId) {
 // the worker pick it up on the next tick. Resets the attempt count so a retry
 // after a config fix gets a full budget again.
 async function resetLeg(postId, leg) {
-  if (!db.LEGS.includes(leg)) throw new Error(`unknown announce leg: ${leg}`)
+  if (!registries.announceLeg(leg)) throw new Error(`unknown announce leg: ${leg}`)
   const job = await db.findByPostId(postId)
   if (!job) return null
+  // A job enqueued before this leg was registered has no row for it; create it so
+  // the retry button works on an existing post after a module is installed.
+  await db.ensureLegs(job.id, [leg])
   await db.updateLeg(job.id, leg, { status: 'pending', attempts: 0, lastError: null, nextAttemptAt: null })
   log.info('announce leg reset for retry', { jobId: job.id, postId, leg })
-  return refreshStatus(job.id)
+  // Labelled, because this is the response body the admin panel re-renders from.
+  return withLabels(await refreshStatus(job.id))
+}
+
+// Decorate a job's legs with the label their registration carries, so the admin
+// panel renders a module's leg with a real name and no client change
+// (MODULE_SYSTEM.md §1.8). An unregistered leg — a stale row from a module that
+// was since removed — keeps its id as the label rather than disappearing.
+function withLabels(job) {
+  if (!job) return job
+  job.legs = (job.legs || []).map((l) => {
+    const registered = registries.announceLeg(l.leg)
+    return { ...l, label: registered ? registered.label : l.leg }
+  })
+  return job
 }
 
 async function getByPostId(postId) {
-  return db.findByPostId(postId)
+  return withLabels(await db.findByPostId(postId))
 }
 
 module.exports = {
@@ -113,4 +133,5 @@ module.exports = {
   refreshStatus,
   resetLeg,
   getByPostId,
+  withLabels,
 }