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/swarm-ui/src/pages/agents/AgentsPage.tsx

@@ -26,6 +26,7 @@
 // see its own comment) — `viewMode` here just says which one to show.
 import { useState } from "preact/hooks";
 import type { ComponentChildren } from "preact";
+import { useLocation } from "wouter-preact";
 import { ApiErrorPanel } from "@hive/shared/api-error-panel.js";
 import { readApiError, type ProblemDetails } from "@hive/shared/api-error.js";
 import { Badge } from "@hive/shared/badge.js";
@@ -95,6 +96,7 @@ type ViewMode = "cards" | "table";
 const VIEW_MODE_KEY = "swarm-ui:agents:view-mode";
 
 export function AgentsPage() {
+  const [, navigate] = useLocation();
   const [rows, setRows] = useState<AgentRow[] | null>(null);
   const [error, setError] = useState<ProblemDetails | null>(null);
   const [intervalMs, setIntervalMs] =
@@ -564,6 +566,17 @@ export function AgentsPage() {
                   </dd>
                 </dl>
                 <div class="ui-agent-detail-actions">
+                  <Badge
+                    variant="quiet"
+                    icon="🖥️"
+                    value="terminal"
+                    onClick={() =>
+                      navigate(
+                        `/agents/${encodeURIComponent(detailTarget.name)}/term`,
+                      )
+                    }
+                    title={`view ${detailTarget.name}'s live terminal`}
+                  />
                   <Badge
                     variant="quiet"
                     icon={<LinkIcon />}