refactor(plugins/platforms): migrate IRC + Teams to new env_enablement + cron_deliver hooks

Adopt the generic platform-plugin hooks landed in the preceding commit
so IRC and Teams get env-only config detection and cron home-channel
delivery without living in cron/scheduler.py's hardcoded sets.

IRC (plugins/platforms/irc/):
- adapter.py: new _env_enablement() seeds server, channel, port,
  nickname, use_tls, server_password, nickserv_password, and a
  home_channel dict into PlatformConfig on env-only setups.
  IRC_HOME_CHANNEL defaults to IRC_CHANNEL so deliver=irc cron jobs
  route to the joined channel by default.
- adapter.py: register_platform() gains env_enablement_fn=_env_enablement
  and cron_deliver_env_var='IRC_HOME_CHANNEL'.
- plugin.yaml: rich requires_env / optional_env with description,
  prompt, password, url for every IRC env var.  Hardcoded IRC entries
  in hermes_cli/config.py still win (back-compat), but the plugin now
  carries its own metadata.

Teams (plugins/platforms/teams/):
- adapter.py: new _env_enablement() seeds client_id, client_secret,
  tenant_id, port, and home_channel into PlatformConfig.  Closes the
  long-standing gap where TEAMS_HOME_CHANNEL was documented but never
  wired up.
- adapter.py: register_platform() gains env_enablement_fn=_env_enablement
  and cron_deliver_env_var='TEAMS_HOME_CHANNEL' — deliver=teams cron
  jobs now work.
- plugin.yaml: rich requires_env / optional_env with description,
  prompt, password, url for every Teams env var.  Surfaces them in
  'hermes config' UI for the first time (Teams had no OPTIONAL_ENV_VARS
  entries before this).

Zero behavior change for existing users: env_enablement_fn is only
called when env vars are set, and the registry's config-first-env-fallback
path in validate_config / is_connected is unchanged.

plugins/platforms/irc/plugin.yaml

@@ -1,4 +1,5 @@
 name: irc-platform
+label: IRC
 kind: platform
 version: 1.0.0
 description: >
@@ -7,7 +8,47 @@ description: >
   (or DMs) and the Hermes agent.  No external dependencies — uses
   Python's stdlib asyncio for the IRC protocol.
 author: Nous Research
+# ``requires_env`` entries are surfaced in ``hermes config`` UI via the
+# platform-plugin env var injector in ``hermes_cli/config.py``.
 requires_env:
-  - IRC_SERVER
-  - IRC_CHANNEL
-  - IRC_NICKNAME
+  - name: IRC_SERVER
+    description: "IRC server hostname (e.g. irc.libera.chat)"
+    prompt: "IRC server"
+    password: false
+  - name: IRC_CHANNEL
+    description: "Channel to join (e.g. #hermes — comma-separate for multiple)"
+    prompt: "IRC channel"
+    password: false
+  - name: IRC_NICKNAME
+    description: "Bot nickname on IRC (default: hermes-bot)"
+    prompt: "Bot nickname"
+    password: false
+optional_env:
+  - name: IRC_PORT
+    description: "IRC server port (default: 6697 with TLS, 6667 without)"
+    prompt: "IRC port"
+    password: false
+  - name: IRC_USE_TLS
+    description: "Use TLS for the IRC connection (1/true/yes to enable, default: true on port 6697)"
+    prompt: "Use TLS? (true/false)"
+    password: false
+  - name: IRC_SERVER_PASSWORD
+    description: "Server password for the IRC PASS command (optional)"
+    prompt: "Server password (optional)"
+    password: true
+  - name: IRC_NICKSERV_PASSWORD
+    description: "NickServ password for automatic IDENTIFY on connect (optional)"
+    prompt: "NickServ password (optional)"
+    password: true
+  - name: IRC_ALLOWED_USERS
+    description: "Comma-separated IRC nicks allowed to talk to the bot"
+    prompt: "Allowed nicks (comma-separated)"
+    password: false
+  - name: IRC_ALLOW_ALL_USERS
+    description: "Allow anyone in the channel to talk to the bot (dev only)"
+    prompt: "Allow all users? (true/false)"
+    password: false
+  - name: IRC_HOME_CHANNEL
+    description: "Channel for cron / notification delivery (defaults to IRC_CHANNEL)"
+    prompt: "Home channel (or empty)"
+    password: false