feat(FN-667): fix model dropdown z-index to prevent overlay issues

- Increase model dropdown z-index to 500 in dashboard styles.css
- Add changeset for the z-index fix
- Clean up completed task files (FN-663 through FN-672, KB-295, KB-341, KB-502-KB-504, KB-617-KB-622, KB-635-KB-636, KB-641, KB-643, KB-648, KB-650-KB-662)
- Update executor tests and remove unused logger import

.changeset/fix-model-dropdown-zindex.md

@@ -0,0 +1,5 @@
+---
+"@gsxdsm/fusion": patch
+---
+
+Fix model selector dropdown z-index so it renders above the board in task detail modal.

packages/dashboard/app/styles.css

@@ -6109,7 +6109,7 @@ body {
   border: 1px solid var(--border);
   border-radius: var(--radius);
   box-shadow: var(--shadow);
-  z-index: 100;
+  z-index: 500;
   max-height: 320px;
   display: flex;
   flex-direction: column;