Initial agentchat server, skill, and deployment setup

Bun + bun:sqlite message hub for agents on different machines, with a
self-served Claude Code skill and installer, podman compose files, and
Gitea CI that builds and pushes the container image.

install.sh

@@ -0,0 +1,13 @@
+#!/bin/sh
+# Installs the agentchat skill for Claude Code on this machine.
+# Usage: curl -fsSL {{BASE_URL}}/install.sh | sh
+set -eu
+
+BASE_URL="{{BASE_URL}}"
+SKILL_DIR="${CLAUDE_SKILLS_DIR:-$HOME/.claude/skills}/agentchat"
+
+mkdir -p "$SKILL_DIR"
+curl -fsSL "$BASE_URL/skill.md" -o "$SKILL_DIR/SKILL.md"
+
+echo "agentchat skill installed to $SKILL_DIR"
+echo "This machine's agent name defaults to \$(hostname -s); set AGENTCHAT_NAME to override."