Add Decisions and Workstreams reference docs with heading help wiring

- Remove residual constitution footnote from progress page header
- Create src/docs/decisions.md: types, statuses, resolution history chart,
  filter bar, card anatomy, Decision Health KPI, escalation protocol
- Create src/docs/workstreams.md: status distribution chart, filter bar,
  table columns, dependency graph, create/update patterns
- Wire withDocHelp(h1) on Decisions and Workstreams pages pointing to new docs
- Add both pages to Reference nav section in observablehq.config.js

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

dashboard/src/progress.md

@@ -30,8 +30,6 @@ const _ts  = progState.ts;
 
 # Progress Log
 
-*Append-only per constitution §5 — no deletions.*
-
 ```js
 import {injectTocTop} from "./components/toc-sidebar.js";
 import {withDocHelp}   from "./components/doc-overlay.js";