feat: Hermes Zulip native platform plugin — deprecates old standalone service

Builds on the NousResearch Hermes Agent plugin system:

- plugins/platforms/zulip/ — full BasePlatformAdapter implementation
  - Zulip event queue polling (like pi-zulip-extension)
  - DM-first + @mention + @all-bots routing
  - Placeholder→edit streaming UX
  - Typing indicators
  - Deduplication and echo-loop prevention
  - Auto-registers via register(ctx) — zero core changes
  - plugin.yaml with full env var schema
- hermes-zulip-plugin/DEPRECATED.md — migration guide from old subprocess-based service

Configuration:
  Env vars: ZULIP_SITE, ZULIP_EMAIL, ZULIP_API_KEY (required)
  Config: platforms.zulip.extra in Hermes config.yaml

plugins/platforms/zulip/plugin.yaml

@@ -0,0 +1,56 @@
+name: zulip-platform
+label: Zulip
+kind: platform
+version: 1.0.0
+description: >
+  Zulip messaging platform adapter for Hermes Agent. Connects to a Zulip
+  server via event queue polling, processes DMs and @mentions, and sends
+  replies with placeholder→edit streaming. Uses the official zulip-js
+  HTTP API pattern (polling, not WebSockets) — lightweight, no external
+  SDK beyond httpx.
+
+author: Syslog Solution LLC
+
+requires_env:
+  - name: ZULIP_SITE
+    description: "Zulip server URL (e.g. https://chat.sysloggh.net)"
+    prompt: "Zulip server URL"
+    password: false
+  - name: ZULIP_EMAIL
+    description: "Bot email address (e.g. tanko-bot@chat.sysloggh.net)"
+    prompt: "Zulip bot email"
+    password: false
+  - name: ZULIP_API_KEY
+    description: "Zulip bot API key"
+    prompt: "Zulip API key"
+    password: true
+
+optional_env:
+  - name: ZULIP_STREAM
+    description: "Primary stream to subscribe to (default: agent-hub)"
+    prompt: "Zulip stream name"
+    password: false
+  - name: ZULIP_ALL_BOTS_USER_ID
+    description: "User ID of the @all-bots user (default: 1)"
+    prompt: "All Bots user ID"
+    password: false
+  - name: ZULIP_AGENT_NAME
+    description: "Agent display name for logging (default: hermes-agent)"
+    prompt: "Agent name"
+    password: false
+  - name: ZULIP_OWNER_EMAIL
+    description: "Owner email for private topic ACL"
+    prompt: "Owner email"
+    password: false
+  - name: ZULIP_POLL_INTERVAL
+    description: "Event poll interval in seconds (default: 3)"
+    prompt: "Poll interval (seconds)"
+    password: false
+  - name: ZULIP_HOME_CHANNEL
+    description: "Default recipient for cron / notification delivery"
+    prompt: "Home channel (email or stream:topic)"
+    password: false
+  - name: ZULIP_HOME_CHANNEL_NAME
+    description: "Human label for the home channel"
+    prompt: "Home channel display name"
+    password: false