feat(dashboard): Interventions page improvements and action-confirm modal

- Move Interventions under Workstreams in the navigator
- Add action-confirm.js: shared modal component for actions requiring a
  mandatory comment (survives live-poll re-renders, unlike inline DOM mutation)
- Wire action-confirm into Interventions (Mark done) and Decisions (Resolve)
- Fix Interventions completed section: fetch all tasks and filter client-side
  so resolved interventions (needs_human=false) still appear under Completed
- Add docs/interventions.md help page with ? button on the h1
- Replace all hardcoded "Bernd" with "human" across dashboard src and docs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

dashboard/observablehq.config.js

@@ -5,7 +5,6 @@ export default {
     // ── Overview ──────────────────────────────────────────────────────────────
     { name: "Overview",       path: "/" },
     { name: "Todo",           path: "/todo" },
-    { name: "Interventions",  path: "/interventions" },
     // ── Organizational Entity Views ───────────────────────────────────────────
     { name: "Domains", path: "/domains" },
     { name: "Repos",   path: "/repos" },
@@ -15,11 +14,12 @@ export default {
       collapsible: true,
       open: false,
       pages: [
-        { name: "Decisions",    path: "/decisions" },
-        { name: "Tasks",        path: "/tasks" },
-        { name: "Debt",         path: "/techdept" },
-        { name: "Extends",      path: "/extensions" },
-        { name: "Dependencies", path: "/dependencies" },
+        { name: "Decisions",     path: "/decisions" },
+        { name: "Tasks",         path: "/tasks" },
+        { name: "Interventions", path: "/interventions" },
+        { name: "Debt",          path: "/techdept" },
+        { name: "Extends",       path: "/extensions" },
+        { name: "Dependencies",  path: "/dependencies" },
       ],
     },
     // ── Functional Report Views ────────────────────────────────────────────────
@@ -49,6 +49,7 @@ export default {
         { name: "Domains",                  path: "/docs/domains" },
         { name: "Extension Points",         path: "/docs/extensions" },
         { name: "Inter-Repo Communication", path: "/docs/inter-repo-communication" },
+        { name: "Interventions",            path: "/docs/interventions" },
         { name: "Live Data",                path: "/docs/live-data" },
         { name: "Overview",                 path: "/docs/overview" },
         { name: "Progress Log",             path: "/docs/progress-log" },