Grow the demo fleet to fifty hosts and a real Windows tier

Twelve hosts running six services read as somebody's side project. Fifty
hosts across twenty-one services read as an estate, which is what a
visitor is trying to see themselves in.

Thirty-one Linux, eighteen Windows, one Linux host whose agent is gone.
The proportions are the point: Windows now carries Active Directory, IIS,
SQL Server, Exchange, file shares, Remote Desktop, print, WSUS and SCCM
rather than appearing as a Security channel on one box. Linux gains a
load-balancer tier, an outbound proxy, MySQL beside Postgres, RabbitMQ,
Elasticsearch, three Kubernetes nodes, CI, Vault, OpenLDAP, BIND and a
backup server.

Fifteen new generators, each writing what the real daemon writes --
HAProxy's timing quintuple, MySQL slow-query blocks, W3C extended format
for IIS, kubelet PLEG lines, BIND query logging with NXDOMAIN, Squid's
TCP_DENIED, SQL Server deadlock and I/O-stall messages -- with the
structured fields carried in attributes so both halves of the query
language have something to work on.

Three things found while doing it, each of which would have shipped as a
quiet wrongness:

linuxHosts() decided Windows by `service == "eventlog"`. That held while
eventlog was the only Windows role; with IIS and SQL Server on Windows it
would have given every one of them a journald system stream -- sshd and
UFW lines on a Windows box. It now decides from `os`.

worker-02 lost its filling disk when the fleet was rewritten, which is
the story worker-disk-filling thresholds on. Restored at its original
rate, with a comment saying why it cannot move.

Five dashboard panels were written as `timechart`, which this query
language does not have -- its stages are where/stats/sort/fields/head/
tail. They are raw ClickHouse SQL now, which the reference recommends for
exactly this, and a `pie` panel was dropped before it shipped because the
web's VizType union has no such member even though the API accepts one.

Five new dashboards: platform/Kubernetes, directory and DNS, messaging
and search, the Windows server estate, and edge/proxy. Every panel was
checked against the language's real stage list and the web's real viz
types.

Volume roughly quadruples: about 316 records/minute at rate-scale 1, and
1.9M per nightly reset at the demo's own settings against about 0.5M
before. ClickHouse will not notice; reset time and disk on the demo box
might, so the README says so and names RATE_SCALE as the lever.

hack/demo-seed/README.md

@@ -23,6 +23,40 @@ other code.
   the demo, `/hack/demo-simulator`. Installed at `/etc/systemd/system/`
   on the demo box.
 
+## The fleet
+
+Fifty hosts, shaped like an estate rather than a stack: thirty-one Linux,
+eighteen Windows, and one Linux host whose agent is gone so the Agents
+page has something stale to show.
+
+| Tier | Hosts |
+|---|---|
+| Edge and proxy | `lb-01/02` (HAProxy), `edge-01/02` (nginx), `proxy-01` (Squid) |
+| Application | `api-01`–`04`, `worker-01`–`03`, `arm-build-01` (aarch64) |
+| Data | `db-01/02` (Postgres), `mysql-01`, `cache-01/02` (Redis), `mq-01/02` (RabbitMQ), `search-01/02` (Elasticsearch) |
+| Platform | `k8s-node-01`–`03` (kubelet), `ci-01` (Jenkins), `vault-01`, `ldap-01` (OpenLDAP), `dns-01` (BIND), `backup-01`, `mail-01` |
+| Windows | `DC-01/02`, `IIS-01`–`03`, `WIN-SQL-01/02`, `EXCH-01/02`, `FS-01/02`, `RDS-01/02`, `WIN-APP-01/02`, `PRINT-01`, `WSUS-01`, `SCCM-01` |
+
+The Windows share is the point of the proportions. An enterprise looking
+at this should recognise its own estate, which means Windows carrying
+real services -- Active Directory, IIS, SQL Server, Exchange, file
+shares, Remote Desktop, print, WSUS and SCCM -- rather than appearing
+only as a Security channel on one box.
+
+Two hosts carry stories the alert rules fire on and must not be moved:
+`worker-02`'s disk fills at 0.04 of the volume per day, which is what
+`worker-disk-filling` thresholds against, and `legacy-01` checks in once
+and goes quiet, which is what `agent-legacy-01-unavailable` catches.
+`api-02` is the host the outage window hits.
+
+**Volume.** Fifty hosts generate about 316 records/minute at
+`-rate-scale 1`, and the nightly reset runs at `RATE_SCALE=0.5` over a
+168-hour backfill -- roughly **1.9M records per reset**, against about
+0.5M when the fleet was twelve hosts. ClickHouse is untroubled by that;
+what it costs is reset time and disk on the demo box. `RATE_SCALE` is the
+lever if either becomes a problem, and lowering it keeps every host and
+service present rather than dropping any of them.
+
 ## Prefilled login
 
 The demo's login page comes up with the read-only `demo` account already