SEV-408: combobox displayValue option (show code, search by label) v0.5.0

When displayValue:true, the input shows the selected option's value (e.g. a
state code "TX") while the dropdown stays label-searchable ("Texas") — for a
field searched by name but displayed compactly. Backward-compatible
(default false). 20/20 tests pass.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@switchev/web-shared",
-  "version": "0.4.0",
+  "version": "0.5.0",
   "description": "Shared browser helpers (formatters, markdown, image polling, combobox) for the SwitchEV frontends",
   "type": "module",
   "exports": {