feat(design): surface phase PR 3 — Chat surface polish

Per the surface-phase spec for the Chat cluster (ChatView, ChatPanel,
ChatMessage, ChatInputBar, ToolCallCard):

Long-form line-height
- ChatMessage: assistant-bubble .message-content jumps from 1.55 to
  1.7 — chat is a reading surface, not a snippet stream. User
  bubbles stay tighter.
- JournalView: dropped its :deep(.role-assistant .message-content)
  override; ChatMessage handles it now and Journal inherits.

ToolCallCard borders
- Removed the outer 1px border. ToolCallCard always renders inside
  an assistant bubble; the bubble already contains it. Background
  tint differentiates without re-bordering. Per the
  structural-not-decorative rule.
- Error state preserved as a 3px left-edge accent in --color-danger,
  mirroring the assistant bubble's own left-edge pattern.

Button reclassification per Hybrid rule
- ChatView .bulk-link "All"/"None": accent text → --color-text-secondary
  (these are tertiary list-control affordances, not brand moments)
- ChatView .bulk-delete-btn: --color-danger (Error terracotta) →
  --color-action-destructive (Oxblood) per Hybrid; paired with a
  Trash2 icon since destructive should always be reinforced by an
  icon, not just color
- ChatView .btn-delete-conv hover: same Error → Oxblood swap
- .btn-new-conv stays accent (brand moment, correct already)
- .btn-send stays accent gradient (primary brand moment, foundation)

Two-weights-only
- Snapped every font-weight: 600/700 to 500 across ChatView,
  ChatPanel, ChatMessage, ToolCallCard per the doc rule.

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

frontend/src/components/ToolCallCard.vue

@@ -532,10 +532,13 @@ function closeEventSlideOver(changed = false) {
 </template>
 
 <style scoped>
+/* Inline ToolCallCard renders inside an assistant bubble — the bubble
+   already contains it, so no outer border per the structural-not-decorative
+   rule. Background tint differentiates it; error state gets a left-edge
+   accent the way the assistant bubble itself uses one. */
 .tool-call-card {
   display: inline-block;
   background: var(--color-bg-secondary);
-  border: 1px solid var(--color-border);
   border-radius: 10px;
   font-size: 0.8rem;
   margin-top: 0.4rem;
@@ -543,7 +546,7 @@ function closeEventSlideOver(changed = false) {
   vertical-align: top;
 }
 .tool-call-card.error {
-  border-color: var(--color-danger, #e74c3c);
+  border-left: 3px solid var(--color-danger);
 }
 .tool-call-card.declined {
   opacity: 0.55;
@@ -566,7 +569,7 @@ function closeEventSlideOver(changed = false) {
 }
 
 .tool-label {
-  font-weight: 600;
+  font-weight: 500;
   color: var(--color-text-muted);
   text-transform: uppercase;
   letter-spacing: 0.03em;
@@ -636,7 +639,7 @@ function closeEventSlideOver(changed = false) {
 }
 .web-search-results .tool-search-item::after { content: none; }
 
-.tool-event-title { font-weight: 600; color: var(--color-text); }
+.tool-event-title { font-weight: 500; color: var(--color-text); }
 .tool-event-time { color: var(--color-text-muted); font-size: 0.75rem; }
 
 .tool-event-list { display: flex; flex-direction: column; gap: 0.2rem; }
@@ -652,7 +655,7 @@ function closeEventSlideOver(changed = false) {
 .tool-note-tag { font-size: 0.72rem; color: var(--color-text-muted); }
 
 .tool-task-priority {
-  font-size: 0.7rem; font-weight: 600; text-transform: uppercase;
+  font-size: 0.7rem; font-weight: 500; text-transform: uppercase;
   letter-spacing: 0.04em; padding: 0.1rem 0.3rem; border-radius: 3px;
 }
 .priority-high { color: var(--color-danger, #e74c3c); }
@@ -697,7 +700,7 @@ function closeEventSlideOver(changed = false) {
 .confirm-created {
   color: var(--color-success, #2ecc71);
   font-size: 0.78rem;
-  font-weight: 600;
+  font-weight: 500;
 }
 .confirm-denied {
   color: var(--color-text-muted);
@@ -792,7 +795,7 @@ function closeEventSlideOver(changed = false) {
 }
 .tool-event-card-title {
   font-size: 0.8rem;
-  font-weight: 600;
+  font-weight: 500;
   color: var(--color-text);
   white-space: nowrap;
   overflow: hidden;