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/device-link.ts

@@ -1,18 +1,20 @@
 import { ClosureComponent, Component } from "mithril";
 import { m } from "../components.ts";
 import { evaluateExpression } from "../store.ts";
+import Expression from "../../lib/common/expression.ts";
 
 const component: ClosureComponent = (): Component => {
   return {
     view: (vnode) => {
       let deviceId;
       const device = vnode.attrs["device"];
-      if (device) deviceId = device["DeviceID.ID"].value[0];
+      if (device) deviceId = device["DeviceID.ID"];
 
       const children = Object.values(vnode.attrs["components"]).map((c) => {
-        if (Array.isArray(c)) c = evaluateExpression(c, device || {});
+        if (c instanceof Expression)
+          c = evaluateExpression(c, device ?? {}).value;
         if (typeof c !== "object") return `${c}`;
-        const type = evaluateExpression(c["type"], device || {});
+        const type = evaluateExpression(c["type"], device ?? {}).value;
         if (!type) return null;
         const attrs = Object.assign({}, vnode.attrs, c);
         return m(type as string, attrs);