fix(builds): add missing start/stop/graceful_stop kind glyphs to QUEUE_KIND_GLYPH

The QueueKind enum has graceful_stop, start, and stop variants but the
dashboard QUEUE_KIND_GLYPH map only covered rebuild/meta_update/spawn/
destroy/restart/startup_sweep/perm_change — the three missing kinds
rendered as '?' in the build queue UI.

This became visible with the deferred start-after-rebuild change: a fast-lane
Start entry now appears as a child of its Rebuild parent, but showed the
fallback '?' glyph.

Glyphs assigned: graceful_stop=⏹, start=▶, stop=■.

Also update the dashboard.md kind-glyph list to include all nine kinds and
note that deferred start-after-rebuild entries also use parent_id grouping.

frontend/packages/dashboard/src/builds.js

@@ -128,6 +128,9 @@ const QUEUE_KIND_GLYPH = {
   restart: '↺',
   startup_sweep: '⚡',
   perm_change: '🔑',
+  graceful_stop: '⏹',
+  start: '▶',
+  stop: '■',
 };
 const QUEUE_STATE_GLYPH = {
   queued: '⏸',