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/summon-button.ts

@@ -1,13 +1,20 @@
-import { ClosureComponent, Component } from "mithril";
+import { ClosureComponent } from "mithril";
 import { m } from "../components.ts";
 import * as taskQueue from "../task-queue.ts";
 import * as store from "../store.ts";
 import * as notifications from "../notifications.ts";
+import Expression from "../../lib/common/expression.ts";
+import { FlatDevice } from "../../lib/ui/db.ts";
 
-const component: ClosureComponent = (): Component => {
+interface Attrs {
+  device: FlatDevice;
+  parameters: Record<string, Expression>;
+}
+
+const component: ClosureComponent<Attrs> = () => {
   return {
     view: (vnode) => {
-      const device = vnode.attrs["device"];
+      const device = vnode.attrs.device;
 
       return m(
         "button",
@@ -19,15 +26,16 @@ const component: ClosureComponent = (): Component => {
             e.target.disabled = true;
             const params = Object.values(vnode.attrs["parameters"])
               .map((exp) => {
-                if (!Array.isArray(exp) || exp[0] !== "PARAM") return null;
-                return store.evaluateExpression(exp[1], device) as string;
+                if (exp instanceof Expression.Parameter)
+                  return exp.path.toString();
+                return null;
               })
               .filter((exp) => !!exp);
 
             const task = {
               name: "getParameterValues",
               parameterNames: params,
-              device: device["DeviceID.ID"].value[0],
+              device: device["DeviceID.ID"] as string,
             };
 
             taskQueue