swarm-ui: read-only agent terminal page consuming the swarm term stream

Moves the TermMsg rendering pipeline (Row.tsx, termMsg.ts, linkify.tsx,
markdown.ts) from @hive/agent into @hive/shared, so swarm-ui becomes a
second consumer of it instead of forking a copy -- CSS was already
shared (@hive/shared/terminal.css). marked+dompurify move from
@hive/agent's deps to @hive/shared's; swarm-ui picks them up
transitively, no new direct dep there.

New swarm-ui route /agents/:name/term (AgentTermPage), linked from
AgentsPage's detail panel via a "terminal" badge next to "link matrix
account". Consumes GET /api/agents/{name}/term/stream: unlike
@hive/agent's own useLiveStream (TermEnvelope-wrapped, history/backfill
dance), the swarm relay forwards one bare TermMsg per SSE event with no
envelope and no history endpoint -- useSwarmTermStream is a much
smaller hook for that shape (EventSource -> parse -> coalesce, nothing
to buffer/dedupe/backfill against).

Verified against a live SSE mock (screenshots in /agents/iris/state/screenshots/
3801-agents-detail-panel-terminal-badge.png and
3801-agent-term-page-live-rows.png -- real rows rendering through the
shared Row component, not just a build/typecheck pass).

frontend/packages/shared/package.json

@@ -6,11 +6,17 @@
   "type": "module",
   "main": "./src/index.js",
   "dependencies": {
+    "dompurify": "^3.2.4",
+    "marked": "18.0.6",
     "preact": "10.29.8"
   },
   "exports": {
     ".": "./src/index.js",
     "./terminal.js": "./src/terminal/terminal.js",
+    "./term-msg.js": "./src/terminal/termMsg.ts",
+    "./term-row.js": "./src/terminal/Row.tsx",
+    "./term-linkify.js": "./src/terminal/linkify.tsx",
+    "./term-markdown.js": "./src/terminal/markdown.ts",
     "./tabs.js": "./src/tabs/tabs.js",
     "./tabs.css": "./src/tabs/tabs.css",
     "./hive-tab-strip.js": "./src/tabs/hive-tab-strip.js",