feat(optimize): support state diagrams in the Optimize panel

Extend the Diagram Doctor beyond flowcharts to stateDiagram / stateDiagram-v2.

- New parseStateDiagram: states → nodes, transitions → edges in source order
  (including `[*]` pseudo-transitions, so linkStyle indices stay aligned);
  `[*]` itself is never a node. Composite states map to groups, notes are
  skipped. A parseDiagram() dispatcher feeds analyze/transforms.
- Fixes are tailored per kind (verified empirically against Mermaid 11):
  * ELK is flowchart-only (state diagrams reject `layout: elk`), so it's not
    offered and the no-ELK score penalty is skipped for state diagrams.
  * Spacing uses the `state` config key; direction is set via a `direction`
    statement rather than the header.
  * State diagrams can't style individual transitions — a `linkStyle` line
    renders as a stray node — so the dim-hubs fix and focus mode fade the
    busy *states* (e.g. CANCELLED) via classDef/class instead of dimming edges.
    Flowcharts keep edge dimming via linkStyle.
- Panel notice now covers flowcharts & state diagrams.

Verified in-browser: state-diagram dim/focus render with zero junk nodes;
flowchart ELK + linkStyle dimming still intact.

README.md

@@ -25,14 +25,15 @@ TypeScript** frontend using **CodeMirror 6** and **Mermaid 11**.
   counts. Network operations shell out to your system `git`, so they reuse your
   existing credentials (SSH agent, keychain / credential helpers) — no separate
   login.
-- **Optimize panel (Diagram Doctor)** — analyse a tangled flowchart and declutter
-  it in one click: a readability score and metrics (hubs, density, cross-group
-  edges), plus source rewrites for the **ELK layered layout**, extra
-  spacing/curved edges, **de-emphasising cross-cutting hub edges** (event bus,
-  audit, cost-style fan-ins), and removing duplicate edges. A non-destructive
-  **focus mode** spotlights any node and its neighbours so you can read a dense
-  graph without changing it. Every rewrite lands in the editor and is reversible
-  with ⌘Z.
+- **Optimize panel (Diagram Doctor)** — analyse a tangled **flowchart or state
+  diagram** and declutter it in one click: a readability score and metrics
+  (hubs, density, cross-group edges), plus source rewrites for the **ELK layered
+  layout** (flowcharts), extra spacing, a layout-direction toggle,
+  **de-emphasising cross-cutting hubs** (event-bus / audit fan-ins on flowcharts;
+  faded sink states like CANCELLED on state diagrams), and removing duplicate
+  edges. A non-destructive **focus mode** spotlights any node/state and its
+  neighbours so you can read a dense graph without changing it. Every rewrite
+  lands in the editor and is reversible with ⌘Z.
 - **Export** the current diagram to **SVG** or **PNG** (2× scale), or **copy a
   PNG straight to the clipboard**. (PNG/clipboard re-render flowcharts with
   text labels so the bitmap rasterizes cleanly across platforms.)