feat(rust): site-owned permissions — the site is the author, the game is the cache

R2, and the first phase where this module WRITES to a game. Groups and grants are
authored on the website and pushed into each server's own permission store, so
every plugin that already calls `UserHasPermission` honours them with no adapter,
and a wipe stops being a data-loss event.

**Seven org-lead decisions (D28-D34).** A grant is keyed to the website USER and
resolved to every Steam id they have linked at push time (D28); every authored row
carries a scope — a server or `*` (D29); groups are mirrored as real groups rather
than flattened (D30); a holder the site did not author is REPORTED, never undone,
with adopt and revoke offered (D31); one verb, with the plugin diffing locally
(D32); a permission no server has registered is reported unresolved and never
self-registered (D33); authoring is people and groups by hand, with rules deferred
(D34).

**Three sets, and every interesting question is a difference between two.**
`desired − pushed` is what to apply; `pushed − desired` is what to RETIRE, because
the site put it there and has since withdrawn it; `present − desired` is drift. The
middle one is why `rust_perm_pushed` exists: a name in the store that is not in the
desired set is either something the site retired or something a human granted, and
those two have opposite correct answers.

**What lands is not what was sent.** A grant naming a permission the server has not
registered did not land — `GrantUserPermission` no-ops silently — and a member the
store has never seen could not be placed. Neither is recorded as pushed, so the
site never believes it gave a privilege it did not.

The loop asks a cheap question every thirty seconds — does the digest of the
desired set still equal what this server last confirmed — and syncs on a change, a
restart, a wipe, a drift hook, a failed attempt past its backoff, or the
fifteen-minute audit that finds drift on a server nobody has touched.

**This module's first admin page**, because a permission model is the first thing
here that has to be composed rather than configured. What is on it is decided by
what an operator can get wrong: four states are invisible from the game and from a
list of grants, and each is a sentence rather than a number.

Walked end to end against a real core at the pinned ref, the real sidecar, and a
stand-in speaking protocol 4 — including a restart that emptied the store and was
fully re-pushed. Four defects the browser found that 133 green tests did not.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PMH6bw1jXMgbyF3ZWGEzSM

server/router/admin/usersRust.router.js

@@ -30,7 +30,7 @@
 const core = require('../../core')
 
 const express = core.express
-const { param } = core.validator
+const { body, param } = core.validator
 
 const usersRust = require('./usersRust.controller')
 const { validate } = core.middleware
@@ -70,4 +70,62 @@ usersRustRouter.delete(
   usersRust.removeLink,
 )
 
+// ── Phase 7: what this person may do in game ─────────────────────────────
+//
+// The same panel, one section lower. It is here rather than only on the
+// permissions screen because the question an operator actually has is about a
+// PERSON — "why can this player spawn a kit" is asked on their page, not on a
+// list of groups — and because the slot is already the place this module says
+// everything else it knows about one user.
+//
+// Both writes go through the ordinary authored tables and the ordinary loop. A
+// grant made here reaches the game when the mirror next reconciles, which is
+// seconds, and never inside this request.
+
+usersRustRouter.get(
+  '/rust/permissions',
+  // #swagger.tags = ['Admin · Users']
+  // #swagger.summary = 'A user’s Rust privileges (admin only)'
+  // #swagger.description = 'The groups this person is in, the permissions granted to them directly, and the Steam accounts those privileges actually reach. An empty `reaches` means they have linked nothing and hold them on paper only.'
+  // #swagger.security = [{ "cookieAuth": [] }, { "bearerAuth": [] }]
+  // #swagger.parameters['id'] = { in: 'path', required: true, schema: { type: 'integer' }, description: 'User id.' }
+  /* #swagger.responses[200] = { description: 'Their groups and grants', content: { "application/json": { schema: { $ref: "#/components/schemas/RustUserPermissions" } } } } */
+  param('id').isInt(),
+  validate,
+  usersRust.listPermissions,
+)
+
+usersRustRouter.post(
+  '/rust/permissions/grants',
+  // #swagger.tags = ['Admin · Users']
+  // #swagger.summary = 'Grant a Rust permission to this user (admin only)'
+  // #swagger.description = 'Authored against the website account, so it reaches every Steam id they have linked — now and later. `scope` is a server id or `*` for the fleet. The push happens on the mirror’s next pass.'
+  // #swagger.security = [{ "cookieAuth": [] }, { "bearerAuth": [] }]
+  // #swagger.parameters['id'] = { in: 'path', required: true, schema: { type: 'integer' }, description: 'User id.' }
+  /* #swagger.responses[201] = { description: 'Granted' } */
+  /* #swagger.responses[200] = { description: 'They already held it' } */
+  /* #swagger.responses[400] = { description: 'Invalid body, or a scope naming no configured server', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
+  param('id').isInt(),
+  body('permission').isString().matches(/^[a-z0-9][a-z0-9._-]{0,127}$/i),
+  body('scope').optional().isString().isLength({ min: 1, max: 64 }),
+  validate,
+  usersRust.addGrant,
+)
+
+usersRustRouter.delete(
+  '/rust/permissions/grants/:grantId',
+  // #swagger.tags = ['Admin · Users']
+  // #swagger.summary = 'Remove a Rust permission from this user (admin only)'
+  // #swagger.description = 'Scoped to this user as well as to the grant, so a wrong id on the URL removes nothing rather than somebody else’s privilege. The revoke reaches the game on the mirror’s next pass.'
+  // #swagger.security = [{ "cookieAuth": [] }, { "bearerAuth": [] }]
+  // #swagger.parameters['id'] = { in: 'path', required: true, schema: { type: 'integer' }, description: 'User id.' }
+  // #swagger.parameters['grantId'] = { in: 'path', required: true, schema: { type: 'integer' }, description: 'The grant to remove.' }
+  /* #swagger.responses[204] = { description: 'Removed' } */
+  /* #swagger.responses[404] = { description: 'No such grant for this user', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
+  param('id').isInt(),
+  param('grantId').isInt({ min: 1 }).toInt(),
+  validate,
+  usersRust.removeGrant,
+)
+
 module.exports = usersRustRouter