feat(dashboard): nav restructure, full context-help coverage, 11 new ref docs

Navigation:
- New order: Overview · Todo · Domains · Repos · Workstreams (collapsible,
  open:false, with atomic sub-entries: Decisions, Tasks, Debt, Extends,
  Dependencies) · Contributions · SBOM · Progress · Reference (collapsible)
- Reference section gains path:/reference landing page; all 18 doc pages
  listed in nav (alphabetical) and in reference.md table

New pages:
- todo.md — Internal / Ecosystem / Third-party todo classification
- dependencies.md — dependency edge table derived from state/summary
- reference.md — Reference landing page with full doc index

New reference doc pages (11):
  contributions, debt, dependencies, domains, extensions, overview,
  repos, tasks, todo + reference (meta) already added previously

doc-overlay.js — lazy bubblehelp tooltip:
- _titleCache Map + _fetchDocTitle(docPath): on first hover of any ?
  button, fetches the target doc page, parses <h1>, sets btn.title
- Native browser tooltip appears exactly on the ? circle on subsequent hover

Context-help wired on all 14 dashboard pages:
- h1 withDocHelp added to: index, todo, domains, repos, tasks, techdept,
  extensions, dependencies (contributions/workstreams/decisions/sbom/
  progress/reference were already wired)
- domains.md + repos.md: added missing withDocHelp import and live-data link
- tasks/techdept/extensions: removed duplicate _h1 const that caused
  SyntaxError: Identifier '_h1' has already been declared

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

dashboard/src/docs/extensions.md

@@ -0,0 +1,102 @@
+---
+title: Extension Points — Reference
+---
+
+# Extension Points — Reference
+
+The Extension Points page tracks known future enhancement opportunities across
+all six domains — design forks the system *could* take, parked deliberately
+for later consideration rather than acted on immediately.
+
+---
+
+## What is an extension point?
+
+An extension point (EP) captures a place in the design where additional
+capability could be added — an API surface that could be extended, a schema
+that could grow, an integration that could be built. Recording an EP
+acknowledges the opportunity without committing to it.
+
+Extension points are distinct from technical debt: debt is a known compromise
+that should be fixed; EPs are optional future directions that may or may not
+be pursued.
+
+---
+
+## EP types
+
+| Type | Examples |
+|------|---------|
+| **api** | New endpoints, query parameters, response fields |
+| **schema** | New tables, columns, relationships |
+| **mcp** | New MCP tools or resources |
+| **dashboard** | New pages, charts, or components |
+| **architecture** | Structural changes to the system design |
+| **integration** | Connections to external systems |
+| **other** | Anything that doesn't fit the above |
+
+---
+
+## Statuses
+
+| Status | Meaning |
+|--------|---------|
+| **open** | Identified, not yet acted on |
+| **in_progress** | Being implemented as part of an active workstream |
+| **addressed** | The capability has been built |
+| **deferred** | Intentionally postponed |
+| **wont_fix** | Decided not to pursue — kept for documentation |
+
+Items are sorted by status (open → in_progress → deferred → addressed → wont_fix)
+then by priority (critical → high → medium → low).
+
+---
+
+## Priorities
+
+| Priority | Meaning |
+|----------|---------|
+| **critical** | Needed to unblock other work |
+| **high** | High-value enhancement for the near term |
+| **medium** | Would be useful but not urgent |
+| **low** | Speculative or long-horizon idea |
+
+---
+
+## Filters
+
+| Filter | Effect |
+|--------|--------|
+| **Status** | Multi-select |
+| **Priority** | Multi-select |
+| **Domain** | Multi-select |
+| **Type** | Multi-select |
+
+---
+
+## Registering an extension point
+
+Via MCP:
+
+```
+register_extension_point(
+  domain       = "custodian",
+  title        = "Configurable poll interval per dashboard page",
+  ep_type      = "dashboard",
+  priority     = "low",
+  description  = "Each page hard-codes POLL = 15_000. An env var or per-page config would allow slowing down low-priority pages to reduce API load.",
+  location     = "state-hub/dashboard/src/*.md",
+  workstream_id = "<uuid>"   # optional
+)
+```
+
+```
+update_ep_status(ep_uuid="<uuid>", status="addressed")
+```
+
+---
+
+## Human-readable IDs
+
+Each EP carries an ID in the form `EP-<DOMAIN>-NNN` (e.g. `EP-CUST-001`).
+IDs are optional at creation and auto-assigned if omitted.