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/agent/src/hooks/useLiveStream.ts

@@ -16,7 +16,7 @@
 // whole dedup signal, see `TermEnvelope`'s doc in hive-agent's
 // `web_ui/stream.rs`.
 import { useEffect, useRef, useState } from "preact/hooks";
-import type { TermEnvelope, TermRow } from "../lib/termMsg.js";
+import type { TermEnvelope, TermRow } from "@hive/shared/term-msg.js";
 
 export interface UseLiveStreamOptions {
   historyUrl?: string;