Add Badge + Dropdown Preact components, demo on swarm-ui /components

New shared Preact primitives for the per-agent terminal redesign:

- Badge (@hive/shared/badge.js): a labelled status pill. Plain <span>
  when static (e.g. "alive"), a real <button> with a disclosure caret
  when given onClick (e.g. opens a Dropdown, or toggles itself in
  place). Same component either way so a status row reads as one
  consistent set of badges regardless of which are interactive.
- Dropdown (@hive/shared/dropdown.js): a small option list anchored
  directly under whatever opened it (no portal, no native <dialog> —
  see the file comment for why). Closes on outside click or Escape.

This is the fix for the design guide's own named anti-example: the
agent page's model/effort pickers live in the overflow menu while the
current model/effort only show as a disconnected chip. Badge+Dropdown
composed together is that control moved inline, next to what it shows.

Demoed on swarm-ui's /components page: all Badge tones, a label-prefixed
badge, an interactive badge that opens a Dropdown (model-picker shape),
and an interactive badge that toggles itself (pause/resume shape).

Both packages build + tsc --noEmit clean.

frontend/packages/shared/package.json

@@ -36,7 +36,11 @@
     "./api-error-panel.js": "./src/api-error-panel/ApiErrorPanel.tsx",
     "./api-error-panel.css": "./src/api-error-panel/api-error-panel.css",
     "./warn-banner.js": "./src/warn-banner/WarnBanner.tsx",
-    "./warn-banner.css": "./src/warn-banner/WarnBanner.css"
+    "./warn-banner.css": "./src/warn-banner/WarnBanner.css",
+    "./badge.js": "./src/badge/Badge.tsx",
+    "./badge.css": "./src/badge/Badge.css",
+    "./dropdown.js": "./src/dropdown/Dropdown.tsx",
+    "./dropdown.css": "./src/dropdown/Dropdown.css"
   },
   "files": [
     "src/"