refactor: replace array-based expressions with typed class hierarchy

Replace the old Lisp-like array expression representation
(["AND", ["PARAM", ...], ...]) with a class hierarchy rooted in
an abstract Expression class (Literal, Parameter, Binary, Unary,
FunctionCall, Conditional). This gives compile-time type safety
to expression construction, evaluation, and pattern matching.

Key changes:
- New lib/common/expression.ts defines the class hierarchy with
  map/evaluate/toString methods
- Rewrite parser as hand-rolled recursive descent, removing the
  parsimmon dependency
- Extend Path with a colon separator to unify parameter identity
  and attributes into a single address space (e.g.
  "Device.WiFi.SSID.1.Name:writable"). The colon field tracks
  how many trailing segments are attribute qualifiers. PathSet
  rewritten with separate param/attr segment indexes
- Flatten device attribute representation in the UI to
  colon-delimited keys mirroring the new path syntax

ui/components/overview-dot.ts

@@ -1,20 +1,23 @@
 import { ClosureComponent, Component } from "mithril";
 import { m } from "../components.ts";
-import config from "../config.ts";
+import { overview } from "../config.ts";
 import { evaluateExpression } from "../store.ts";
 
-const CHARTS = config.ui.overview.charts;
+const CHARTS = overview.charts;
 
 const component: ClosureComponent = (): Component => {
   return {
     view: (vnode) => {
       const device = vnode.attrs["device"];
-      const chartName = evaluateExpression(vnode.attrs["chart"], device || {});
-      const chart = CHARTS[chartName as string] as Record<string, unknown>;
+      const chartName = evaluateExpression(
+        vnode.attrs["chart"],
+        device ?? {},
+      ).value;
+      const chart = CHARTS[chartName as string];
       if (!chart) return null;
-      for (const slice of Object.values(chart.slices)) {
-        const filter = slice["filter"];
-        if (evaluateExpression(filter, device || {})) {
+      for (const slice of chart.slices) {
+        const filter = slice.filter;
+        if (evaluateExpression(filter, device ?? {}).value) {
           const dot = m(
             "svg.inline",
             {
@@ -28,10 +31,10 @@ const component: ClosureComponent = (): Component => {
               cx: "0.5em",
               cy: "0.5em",
               r: "0.4em",
-              fill: evaluateExpression(slice["color"], null),
+              fill: slice.color,
             }),
           );
-          return m("span", dot, evaluateExpression(slice["label"], null));
+          return m("span", dot, slice.label);
         }
       }
       return null;