fix(client): restore feed-tabs CSS + MD paragraph separator

Two regressions flagged in code review:

C1 — .feed-tabs/.feed-tab/.feed-tab.active rules were accidentally
deleted alongside the selection-styling cleanup in 170b455. The
HEAD markup in ActivityFeedHeader.tsx still emits those classes
for the All/By Agent toggle, so the tabs were rendering unstyled.
Restored the rules from 62e4b50 as-is.

C2 — The ReactMarkdown `p` renderer emitted a bare fragment, which
caused multi-paragraph messages ("foo\n\nbar") to render as
"foobar" with no separator. Now emits a trailing space so adjacent
paragraphs collapse via white-space:normal into one space between
them, preserving the inline flow.

Author: FulAppiOS

client/src/components/ActivityFeed.css

@@ -80,6 +80,31 @@
 
 .feed-spacer { flex: 1; }
 
+.feed-tabs {
+  display: flex;
+  gap: 2px;
+  background: rgba(0, 0, 0, 0.25);
+  border-radius: 4px;
+  padding: 2px;
+}
+.feed-tab {
+  padding: 3px 10px;
+  font-size: 12px;
+  color: var(--feed-pergamena);
+  opacity: 0.6;
+  border: none;
+  background: transparent;
+  border-radius: 3px;
+  cursor: pointer;
+  font-family: inherit;
+}
+.feed-tab.active {
+  background: rgba(196, 163, 90, 0.3);
+  color: #fff;
+  opacity: 1;
+  font-weight: bold;
+}
+
 .feed-fold-buttons { display: flex; gap: 4px; }
 .feed-fold-btn {
   width: 26px; height: 24px;

client/src/components/ActivityRow.tsx

@@ -6,10 +6,11 @@ import { isError, isPath, resolvePath, categorizeEntry } from './activityFeedUti
 import type { ActionFilter } from './activityFeedUtils';
 
 // Message cells render detail as markdown (bold, italic, code, links). The
-// custom `p` renderer emits a fragment so multiple paragraphs flow inline —
-// no extra vertical space, no visible paragraph breaks.
+// custom `p` renderer emits the children followed by a trailing space so
+// multiple paragraphs flow inline with a visible word-break between them —
+// no extra vertical space, no paragraphs glued together ("fooBar").
 const MD_COMPONENTS = {
-  p: ({ children }: { children?: ReactNode }) => <>{children}</>,
+  p: ({ children }: { children?: ReactNode }) => <>{children}{' '}</>,
 };
 
 interface ActivityRowProps {