STATE-WP-0072: remediate remaining workstream HTTP callers

Research sweep captured in research/20260709-workstream-caller-sweep.md.
Migrate dashboard detail tasks query, custodian_cli POST bodies, and
onboarding curl to workplan-first paths; re-capture 8h legacy-meter evidence.

dashboard/src/workstreams/[id].md

@@ -14,7 +14,7 @@ const [raw, taskRows, workplanIndex] = await Promise.all([
   fetch(`${API}/workplans/${wsId}`)
     .then(r => r.ok ? r.json() : r.json().then(e => ({error: e.detail ?? `HTTP ${r.status}`})))
     .catch(e => ({error: String(e)})),
-  fetch(`${API}/tasks/?workstream_id=${wsId}&limit=1000`)
+  fetch(`${API}/tasks/?workplan_id=${wsId}&limit=1000`)
     .then(r => r.ok ? r.json() : [])
     .catch(() => []),
   fetch(`${API}/workplans/index`)