docs: split bot.toml.example into per-transport example files

Replace the monolithic bot.toml.example with separate files for each
transport: matrix, whatsapp-meta, whatsapp-twilio, and slack. Add a
chat bot configuration section to the README explaining that only one
transport can be active at a time and how to set up each one.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.storkit/bot.toml.matrix.example

@@ -0,0 +1,26 @@
+# Matrix Transport
+# Copy this file to bot.toml and fill in your values.
+# Only one transport can be active at a time.
+
+enabled = true
+transport = "matrix"
+
+homeserver = "https://matrix.example.com"
+username = "@botname:example.com"
+password = "your-bot-password"
+
+# List one or more rooms to listen in.
+room_ids = ["!roomid:example.com"]
+
+# Users allowed to interact with the bot (fail-closed: empty = nobody).
+allowed_users = ["@youruser:example.com"]
+
+# Bot display name in chat.
+# display_name = "Assistant"
+
+# Maximum conversation turns to remember per room (default: 20).
+# history_size = 20
+
+# Rooms where the bot responds to all messages (not just addressed ones).
+# This list is updated automatically when users toggle ambient mode at runtime.
+# ambient_rooms = ["!roomid:example.com"]