docs: make scaffold server-agnostic

The bot is a universal Minecraft player, not tied to any one server.
Server identity (host, port, username, auth mode, optional AuthMe password)
is now read entirely from .env.

- README: rewritten as universal-bot pitch; auth covered as two dimensions
  (MC auth mode + LLM credential)
- AGENTS.md: identity comes from .env, hard-coded references to pepa
  removed; bootstrap step auto-detects whether the server uses an
  AuthMe-style /register-/login plugin
- .env.example: example values replaced with placeholders, MC_AUTH_MODE
  added (offline | microsoft)
- docs/architecture.md: rephrased target as "any Minecraft Java server",
  added open question on cross-server vs per-server state

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.env.example

@@ -1,19 +1,25 @@
 # --- Minecraft connection -----------------------------------------------------
-# The pepa server. Cracked mode — any nickname works.
-MC_HOST=play.xmatic.team
+# Any Minecraft Java server. The values below are an example — replace them.
+MC_HOST=play.example.com
 MC_PORT=25565
 MC_USERNAME=pepa_pi_bot
-MC_VERSION=auto                # 'auto' lets mineflayer detect the server's version
+MC_VERSION=auto                # 'auto' = let mineflayer detect from server
 
-# --- AuthMe (in-game login) ---------------------------------------------------
-# Used for /register on first join and /login on subsequent joins.
-# Min length is set on the pepa server — keep it ≥ 8 chars.
-# NEVER commit a real value; .env is gitignored.
-MC_AUTHME_PASSWORD=change-me-to-a-long-password
+# --- Minecraft auth -----------------------------------------------------------
+# 'offline'   — cracked servers (server runs with online-mode=false). Any nick works.
+# 'microsoft' — premium / online-mode servers. Mineflayer runs a device-code flow
+#               on first connect and caches the token under ~/.minecraft-auth/.
+MC_AUTH_MODE=offline
+
+# --- Optional: in-game login plugin (AuthMe, nLogin, etc.) --------------------
+# Many cracked servers gate gameplay behind an in-chat /register and /login flow.
+# Leave blank if your target server doesn't use one.
+# Min length is usually 8; use a long random value and never commit it.
+MC_AUTHME_PASSWORD=
 
 # --- LLM provider -------------------------------------------------------------
-# Set ONE of the following. Pi auto-detects from env.
-# OAuth subscriptions (ChatGPT Pro, Claude Max) — leave keys empty and run `pi /login`.
+# Set ONE credential below, OR leave them all blank and run `pi /login` for OAuth
+# (ChatGPT Pro, Claude Max, etc. — when the provider supports it).
 OPENAI_API_KEY=
 ANTHROPIC_API_KEY=
 GOOGLE_API_KEY=
@@ -27,13 +33,14 @@ PI_DEFAULT_MODEL=gpt-5-mini
 # How often (seconds) the autonomous tick prompt fires. Set to 0 to disable.
 TICK_INTERVAL_SECONDS=60
 
-# Chat rate limit (messages per minute). Paper's spam kicker triggers around 20/min.
+# Chat rate limit (messages per minute). Paper/Spigot spam kickers typically
+# trigger around 20/min.
 CHAT_RATE_LIMIT_PER_MIN=15
 
 # --- Operator -----------------------------------------------------------------
 # In-game nick of the human operator. The bot treats their chat messages as
 # higher-priority than other players.
-OPERATOR_USERNAME=halofourteen
+OPERATOR_USERNAME=your_in_game_nick
 
 # --- Optional: Telegram bridge (future skill, not wired yet) ------------------
 # TELEGRAM_BOT_TOKEN=