Make main the lean product a site receives

main was 16 days and 259 commits behind the line the product is actually built
on, at contract 0.30.0 against 0.35.0, with no per-PC credential code at all. It
was neither current nor curated - just stale. This brings it forward and, at the
same time, makes it mean something: main is what a receiving site installs, and
nothing else.

WHAT IT CARRIES. Twelve plugins - backups, computers, endpoints, guides,
knowledgebase, machines, network, notifications, printers, slides, tools,
warranty - plus applications, which is manifest-less core and always ships. The
only manifest dependency inside that set is endpoints on computers, and both are
in it, so the closure is self-contained.

WHAT IT DOES NOT. employees, geenforce, measuringtools, printedparts and usb
stay on the site line. So do the Windows installer tree, the VM rehearsal
helpers, the agent tooling config, one site's data loader, the internal audit
and findings records, and the planner spreadsheet. 1,135 tracked files against
1,438.

A REMOVAL THAT BREAKS THE APP IS NOT A REMOVAL, and two nearly shipped:

deploy/site-profile-universal.json still named all seventeen plugins. It is the
file docs/DEPLOY.md tells a site to provision from, so a fresh install would
have failed at `flask plugin apply-profile` with PluginError - the first thing a
receiving site does, broken by the branch meant to serve them. It now names the
twelve that exist, and its comment says the two must agree.

agent/ was never refreshed. Whoever populated this branch copied shopdb/,
plugins/, frontend/ and tests/ from the site line and left the agent tree at its
September state: 22 C# and PowerShell sources missing, including AgentCredentials,
EnrollmentService, AgentHttpFactory and the fleet-alert client, plus one file the
site line had deleted still present. The old tree is internally consistent, so it
compiles, and nothing in CI builds it - every gate was green over a server that
speaks enrollment and per-PC credentials to a bundled agent source that cannot.
Resynced whole.

DECISIONS THIS ENCODES, rather than defers:

- The plugin-authoring lab builds printedparts, whose manifest depends on
  employees, so it could not stay. The lab remains on the site line and main
  ships no build-along tutorial. That is a real loss for an adopting developer
  and is recorded here rather than discovered later.
- Recognition, Training and Recertification notifications are no longer seeded.
  Each splits one notification into a card per employee and renders a photo,
  which needs a plugin this branch does not bundle. Seeding them would offer an
  author a type that cannot resolve anybody. A site that installs employees gets
  them from that plugin's own seed.
- Windows/IIS is documented as the legacy path throughout, and the README leads
  with Docker, because that is what a receiving site gets.

The API description is regenerated for THIS branch - 347 paths and 483
operations, down from 415 and 573 - so the published contract describes what is
here rather than what the site line serves. docs/CONFIG.md lost the two
measuring-tool label keys the code no longer declares, which two lanes had
decided opposite ways.

Suite: 3124 passed, 6 skipped. Naming and style gates pass. The docs gates run
rather than skip, and every index line count is derived from the file it names.

plugins/computers/plugin.py

@@ -6,7 +6,7 @@ import logging
 from pathlib import Path
 from typing import List, Dict, Optional, Type
 
-from flask import Flask, Blueprint
+from flask import Flask, Blueprint, g
 import click
 
 from shopdb.plugins.base import BasePlugin, PluginMeta
@@ -218,6 +218,16 @@ class ComputersPlugin(BasePlugin):
         self._register_import_hook()
         logger.info(f"Computers plugin initialized (v{self.meta.version})")
 
+    def get_settings_routes(self) -> List[Dict]:
+        """Register Operating Systems management page in Model Catalog."""
+        return [{
+            'hub': 'model-catalog',
+            'path': 'operatingsystems',
+            'name': 'model-catalog-os',
+            'tab': 'Operating Systems',
+            'component': '.plugins-staged/computers/views/OperatingSystemsList.vue'
+        }]
+
     # -- bulk-import machine link -------------------------------------------
 
     def _register_import_hook(self):
@@ -444,6 +454,7 @@ class ComputersPlugin(BasePlugin):
         """
         return {
             'identityfield': 'hostname',
+            'acceptsagentcredential': True,
             'fields': {
                 'hostname': {'type': 'string', 'required': True},
                 'machinenumber': {'type': 'string'},
@@ -714,6 +725,13 @@ class ComputersPlugin(BasePlugin):
             comp = (Computer.query.join(Asset, Asset.assetid == Computer.assetid)
                     .filter(Asset.assetnumber.ilike(hostname)).first())
 
+        # A per-PC credential reports for its own PC only, and never creates one.
+        if (getattr(g, 'agentauth', None) == 'credential'
+                and (comp is None
+                     or comp.assetid != getattr(g, 'agentassetid', None))):
+            raise PermissionError(
+                'The payload names a different endpoint than the credential')
+
         action = 'updated'
         if not comp:
             atype = AssetType.query.filter_by(assettype='computer').first()
@@ -1721,6 +1739,14 @@ class ComputersPlugin(BasePlugin):
                     rel.isactive = False
             return []
 
+        # Plugin-optional by contract, and on this line the option is OFF: no
+        # measuringtools plugin is bundled, so this import always fails and a
+        # metrology PC reports as an ordinary PC with no instrument asset and no
+        # tool link. That is the right answer here - ADR-018 says a CMM is a
+        # machine - and the whole branch stays because the contract is that a
+        # site MAY install a measuringtools plugin of its own, at which point
+        # this adopts and links exactly as it always did. The warning rides back
+        # on the collector response so the silence is at least explained.
         try:
             from plugins.measuringtools.models import MeasuringTool
         except ImportError:
@@ -2307,3 +2333,16 @@ class ComputersPlugin(BasePlugin):
         today should weigh it.
         """
         return ['computers.view']
+
+    def get_asset_type_descriptor(self):
+        """Return descriptor for computer types management in Asset Type Hub."""
+        return {
+            'assettype': 'computer',
+            'subtype_endpoint': '/computers/types',
+            'subtype_id_field': 'computertypeid',
+            'subtype_label_field': 'computertype',
+            'subtype_description_field': 'description',
+            'subtype_color_field': 'color',
+            'optional_tabs': [],
+            'edit_permission': 'computers.manage',
+        }