Show node host figures and history in the node dialog

[SaladDay]

Wires the two backend requests delivered in #108 into the console, verified against a live Core.

• Node dialog (Sandbox metrics):
  • CPU now reads the host's busy share of its cores ("1.3% of 128 cores"), and memory reads used / total, both from the node's last heartbeat.
  • A new Host section charts the machine's CPU busy share and used memory (with its total) over the page's range, from GET /core/v1/sandbox/nodes/{id}?range=1h|6h|24h. Offline buckets stay gaps.
• Client: SandboxAdminClient.retrieveNode(nodeId, range) with the SandboxNodeDetail / SandboxNodeHost types from contracts/agents-api/node-host-history.md.
• Core metrics, now on real data: the header shows a 12-character revision instead of the full 40, and sub-10 ms latencies keep a decimal, so the database axis no longer reads "1 ms" on every tick. The process CPU and resident memory fields from Report Core process metrics and node host history #108 already feed the page (Show Core's CPU and resident memory on Core metrics #100).
• docs/web/protocol-coverage.md lists the node detail read.

Live check: Core built from main (#108), a real Docker node enrolled on this host, and core-console in front of it.

• Core reports host cpu_utilization 0.006 of 128 effective cores and 1 TB total memory, plus 60 one-minute history buckets that fill as heartbeats are sampled.
• Core metrics reports process cpu_cores 0.007 and rss_bytes 26 MB, with its series.
• The console showed both through the real proxy.
• Note: cpu_limit_cores was null there. Core ran in a login-session cgroup without the CPU controller, so cpu.max doesn't exist; the contract keeps unreadable limits null.

Validation: typecheck, 332 web unit tests, 14 browser acceptance tests on headless Chromium (the node dialog test now checks the host figures and chart). Gate and CI results are in the checks.

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