gpuledger v0.5.0

A page to look at: serve shows its node at /, fleet serve shows the cluster from
one process, both server-rendered, refreshing without script, behind GET-only
endpoints and a strict Content-Security-Policy; the fleet view as a Nomad job, run for
real in the matrix — which found that a Consul service keeps a job off a node without
Consul from Nomad 1.3. The driver side, as before, only against a fake nvidia-smi
(GL-10, v0.6.0).

Upgrading from 0.4.0

• Every HTTP endpoint answers GET and HEAD only; anything else is now a 405.
• The job specs take -var consul=false for a cluster without Consul (default on:
  nothing changes where Consul runs).
• fleet serve and deploy/nomad/gpuledger-fleet.nomad.hcl are new; they listen on 9878.

Added

• gpuledger fleet serve: polls the fleet every --interval and serves its page (each
  node linked to its own), /fleet JSON, /metrics with the cluster's totals
  (gpuledger_fleet_*) and /healthz, behind the same GET-only, CSP headers; listens
  on 9878 by default (GL-34).
• deploy/nomad/gpuledger-fleet.nomad.hcl: fleet serve as one service instance,
  discovery as a variable, checksum required. The Nomad matrix runs it with nomad job run on every version, the binary of the commit served locally (GL-35).
• The node's page: serve answers / with the GPUs, their state and since when, who
  reserved and who holds each, and the findings — server-rendered HTML, light and dark,
  refreshing every --interval without a script (GL-33).
• Safe to expose: every endpoint GET and HEAD only (405 otherwise), a
  Content-Security-Policy that allows the page's own stylesheet and nothing else,
  nosniff, no-referrer, X-Frame-Options: DENY, no-store; names escaped by
  context, tested with a container named like a script (GL-36).

Fixed

• On a cluster without Consul, from Nomad 1.3, the system job was never placed: a Consul
  service block adds the constraint ${attr.consul.version} >= 1.8.0. All three job
  specs take -var consul=false, which leaves the registration out. Found by running
  the fleet job in the Nomad matrix.
• The site's navbar wrapped onto a second line and out of the header once the README
  grew to seven sections. It is one line now whatever the README grows to: the sections
  scroll sideways when they do not fit, with a fade only on the side that hides some,
  GitHub pinned outside the scroll, and only the logo and GitHub below 900 px.