[bug] /runtime/status reports the stale default row's node, so the console's connected dot can be flatly wrong #238

Same class as #218, different route — and this one drives what the user sees, so it is how the
console comes to lie about connectivity.

What happens

GET /v1/instances/:instanceId/runtime/status (routes/instances.ts:729) resolves the runner with
requireRuntime → getRuntime, which reads the single default row:

SELECT * FROM instance_runtimes WHERE instance_id = ?1 AND user_id = ?2   -- instances-runtime.ts:621

Per-node truth lives in a different table (instance_runtime_nodes, getRuntimeNode:636). The
default row is overwritten by the newest pags up and is never cleared on disconnect — the
docstring on requireLiveRuntime says so, and says anything that dispatches must use the live,
pin-aware resolver instead.

The route then does:

const relayIsConnected = await relayConnected(c.env, instanceId, runtime.runner_node);  // :754
return c.json({ …, relay: { connected: relayIsConnected, runnerNode: runtime.runner_node } });

So on a multi-machine account it reports the relay state of whichever machine registered last,
not the machine that is live or the one the instance is pinned to.

Why it matters

This response is the console's connectivity signal in two places:

• pages/InstanceDetail.tsx:186 — the header dot: setRunnerOnline(d.relay?.connected === true).
  No fallback. Wrong default row ⇒ the dot is simply wrong.
• tabs/SettingsTab.tsx:163 — agentOnline = relayInfo?.connected === true || pinnedDetail?.connected === true.
  The pinnedDetail fallback partially papers over it, which is likely why this hasn't been
  noticed: Settings can recover where the header cannot.

It also persists the wrong verdict: updateRuntimeStatus(…, effective) at :753 writes a
status derived from probing the wrong node onto the default row, which other callers then read.

Failure shape: pags up on the laptop, then on the desktop (default row → desktop). Desktop
sleeps, laptop still serving. Header dot reads the desktop's dead relay and says offline while
every runner tool works. Reverse the order and it claims online against a machine that is gone.

Expected

Resolve the same way dispatch does — live, pin-aware (getBoundRunnerConn / requireLiveRuntime)
— and report the node it actually resolved, so relay.runnerNode names the machine the verdict is
about. A status endpoint that disagrees with the routing layer is worse than no status endpoint.

Verification

• Two registered nodes, default row stale, live socket on the other: /runtime/status reports
  connected, and relay.runnerNode names the LIVE machine.
• The header dot and Settings agree with each other and with coding_diagnostics.
• Probing does not write an offline status derived from a node that isn't the live one.