chore(ui): remove dead code from navigation redesign

Deleted:
- ScopeTrail component (replaced by inline breadcrumb in TopBar)
- ExchangeList component (replaced by Dashboard DataTable)
- ExchangeDetail page (replaced by inline split view)

Removed from Dashboard:
- flattenProcessors() function (unused after detail panel removal)
- 11 dead CSS classes (panelSection, overviewGrid, errorBlock,
  inspectLink, openDetailLink, filterBar, etc.)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/pages/Dashboard/Dashboard.module.css

@@ -11,11 +11,6 @@
 /* Table section — stretches to fill and scrolls internally */
 
 
-/* Filter bar spacing */
-.filterBar {
-  margin-bottom: 16px;
-}
-
 .tableSection {
   display: flex;
   flex-direction: column;
@@ -166,112 +161,6 @@
   margin-top: 3px;
 }
 
-/* Detail panel sections */
-.panelSection {
-  padding-bottom: 16px;
-  margin-bottom: 16px;
-  border-bottom: 1px solid var(--border-subtle);
-}
-
-.panelSection:last-child {
-  border-bottom: none;
-  margin-bottom: 0;
-  padding-bottom: 0;
-}
-
-.panelSectionTitle {
-  font-size: 11px;
-  font-weight: 600;
-  text-transform: uppercase;
-  letter-spacing: 0.5px;
-  color: var(--text-muted);
-  margin-bottom: 10px;
-  display: flex;
-  align-items: center;
-  gap: 8px;
-}
-
-.panelSectionMeta {
-  margin-left: auto;
-  font-family: var(--font-mono);
-  font-size: 10px;
-  font-weight: 500;
-  text-transform: none;
-  letter-spacing: 0;
-  color: var(--text-faint);
-}
-
-/* Overview grid */
-.overviewGrid {
-  display: flex;
-  flex-direction: column;
-  gap: 8px;
-}
-
-.overviewRow {
-  display: flex;
-  align-items: flex-start;
-  gap: 12px;
-}
-
-.overviewLabel {
-  font-size: 10px;
-  font-weight: 600;
-  text-transform: uppercase;
-  letter-spacing: 0.6px;
-  color: var(--text-muted);
-  width: 90px;
-  flex-shrink: 0;
-  padding-top: 2px;
-}
-
-/* Error block */
-.errorBlock {
-  background: var(--error-bg);
-  border: 1px solid var(--error-border);
-  border-radius: var(--radius-sm);
-  padding: 10px 12px;
-}
-
-.errorClass {
-  font-family: var(--font-mono);
-  font-size: 10px;
-  font-weight: 600;
-  color: var(--error);
-  margin-bottom: 4px;
-}
-
-.errorMessage {
-  font-size: 11px;
-  color: var(--text-secondary);
-  line-height: 1.5;
-  font-family: var(--font-mono);
-  word-break: break-word;
-}
-
-/* Inspect exchange icon in table */
-.inspectLink {
-  background: transparent;
-  border: none;
-  color: var(--text-faint);
-  opacity: 0.75;
-  cursor: pointer;
-  font-size: 13px;
-  padding: 2px 4px;
-  border-radius: var(--radius-sm);
-  line-height: 1;
-  display: inline-flex;
-  align-items: center;
-  justify-content: center;
-  transition: color 0.15s, opacity 0.15s;
-  text-decoration: none;
-}
-
-.inspectLink:hover {
-  color: var(--text-primary);
-  opacity: 1;
-}
-
 /* Attributes cell in table */
 .attrCell {
   display: flex;
@@ -288,20 +177,3 @@
   color: var(--text-muted);
 }
 
-/* Open full details link in panel */
-.openDetailLink {
-  background: transparent;
-  border: none;
-  color: var(--amber);
-  cursor: pointer;
-  font-size: 12px;
-  padding: 0;
-  font-family: var(--font-body);
-  transition: color 0.1s;
-}
-
-.openDetailLink:hover {
-  color: var(--amber-deep);
-  text-decoration: underline;
-  text-underline-offset: 2px;
-}