feat(design): surface phase PR 5 — Project + Workspace polish

Per the surface-phase spec for the Project list, Project view, and
3-panel Workspace cluster:

Button reclassification per Hybrid rule
- ProjectView:
  - btn-workspace ("Open Workspace"): kept on accent gradient — the
    workspace is the project's central feature moment, a Scribe-
    flavored action, brand moment per the doc.
  - btn-share: muted-outline → Bronze action-secondary
  - btn-danger-outline (Delete project): generic-border + danger-on-
    hover → Oxblood outline + filled hover (proper destructive)
  - btn-save-panel: accent gradient → Moss action-primary
  - btn-ms-confirm (milestone confirm): flat accent → Moss
  - btn-ms-cancel: ghost → Bronze action-secondary
  - .modal-btn-danger: --color-danger → --color-action-destructive
- ProjectListView:
  - btn-primary ("+ New Project"): flat accent → Moss action-primary.
    Empty-state CTA (.empty-action) keeps accent — that *is* a
    brand moment per Hybrid, "create your first project".
- WorkspaceTaskPanel + WorkspaceNoteEditor:
  - btn-delete-task / btn-delete: hover --color-danger → Oxblood
  - btn-delete-confirm / btn-confirm-delete: --color-danger pair →
    --color-action-destructive pair, with filled hover for stronger
    affordance
  - btn-save (WorkspaceNoteEditor): flat accent → Moss
- WorkspaceChatWidget:
  - History toggle: replaced unicode ▾ with Lucide ChevronDown
    (PR 1 carry-over for emoji-as-icon)

Two-weights-only
- Snapped every font-weight 600/700 to 500 across the cluster.

Borders kept (per structural-not-decorative rule)
- Milestone group cards: standalone containers, keep
- Project cards in list: standalone containers, keep
- Task slide-over panel: drawer modal, keep
- Workspace 3-panel separators: major section dividers, keep

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/components/WorkspaceTaskPanel.vue

@@ -374,7 +374,7 @@ defineExpose({ reload: loadAll });
   text-transform: uppercase;
   letter-spacing: 0.04em;
   font-size: 0.75rem;
-  font-weight: 600;
+  font-weight: 500;
 }
 
 .task-add {
@@ -433,7 +433,7 @@ defineExpose({ reload: loadAll });
 .ms-group-header:hover { background: color-mix(in srgb, var(--color-primary) 8%, var(--color-surface)); }
 
 .ms-chevron { font-size: 0.6rem; color: var(--color-text-muted); width: 0.8rem; }
-.ms-name { flex: 1; font-weight: 600; font-size: 0.8rem; }
+.ms-name { flex: 1; font-weight: 500; font-size: 0.8rem; }
 .ms-count { font-size: 0.72rem; color: var(--color-text-muted); background: var(--color-bg); border-radius: 10px; padding: 0 0.4rem; }
 
 .ms-status {
@@ -523,7 +523,7 @@ defineExpose({ reload: loadAll });
   padding: 0.2rem 0.55rem;
   border-radius: 12px;
   font-size: 0.75rem;
-  font-weight: 600;
+  font-weight: 500;
   cursor: pointer;
   border: 1.5px solid var(--color-border);
   background: none;
@@ -576,19 +576,21 @@ defineExpose({ reload: loadAll });
   border-radius: 3px;
   margin-left: 0.25rem;
 }
-.btn-delete-task:hover { color: var(--color-danger, #e74c3c); }
+.btn-delete-task:hover { color: var(--color-action-destructive); }
 
 .btn-delete-confirm {
   background: none;
-  border: 1px solid var(--color-danger, #e74c3c);
-  color: var(--color-danger, #e74c3c);
+  border: 1px solid var(--color-action-destructive);
+  color: var(--color-action-destructive);
   font-size: 0.72rem;
-  font-weight: 600;
+  font-weight: 500;
   cursor: pointer;
   padding: 0.15rem 0.5rem;
   border-radius: 4px;
   margin-left: 0.25rem;
+  transition: background 0.15s, color 0.15s;
 }
+.btn-delete-confirm:hover:not(:disabled) { background: var(--color-action-destructive); color: #fff; }
 .btn-delete-confirm:disabled { opacity: 0.5; cursor: default; }
 
 .btn-delete-cancel {
@@ -604,7 +606,7 @@ defineExpose({ reload: loadAll });
 .detail-title {
   padding: 0.75rem 0.75rem 0.25rem;
   font-size: 0.95rem;
-  font-weight: 600;
+  font-weight: 500;
   margin: 0;
   color: var(--color-text);
   flex-shrink: 0;
@@ -673,7 +675,7 @@ defineExpose({ reload: loadAll });
 }
 .task-due.overdue {
   color: var(--color-danger, #e74c3c);
-  font-weight: 600;
+  font-weight: 500;
 }
 
 /* Close detail button */