Added README.

README.md

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+# Crabstero
+
+The simple nonversation Discord bot.
+
+Crabstero is a Discord bot that learns from messages in each channel and uses
+Markov chains to generate responses when it is mentioned.
+
+## Overview
+
+Crabstero is intended for Discord servers that want a lightweight chatbot with
+channel-local, randomly generated replies. It does not use a large language
+model; it learns from the channels it can read and uses that history to assemble
+replies when mentioned.
+
+This repository and README are for running your own instance of Crabstero. To
+invite the official hosted instance instead of running your own bot, see the
+[Crabstero project page](https://logal.dev/projects/crabstero/).
+
+## Features
+
+- Per-channel Markov chain generation for Discord messages.
+- Automatic ingestion of accessible channel history and new messages.
+- Mention-triggered replies based on each channel's learned message history.
+- `/pingme` user control for opting into pings from generated mentions.
+- `/forgetme` user data deletion and future message ingestion opt-out.
+- SQLite-backed storage for learned message data.
+- Optional Prometheus metrics over TCP or a Unix socket.
+- systemd notification and watchdog support when run as a service.
+
+## Requirements
+
+- A Linux host or virtual machine.
+- [uv](https://docs.astral.sh/uv/getting-started/installation/) for Python
+  management and the install/run commands below.
+- A Discord application with a bot token and the Message Content intent enabled.
+- Discord channel permissions to view channels, read message history, and send
+  messages where Crabstero should operate.
+
+## Discord setup
+
+In the [Discord Developer Portal](https://discord.com/developers/applications),
+create an application, add a bot, and enable the Message Content intent for the
+bot. Crabstero reads message content and embed text to learn channel-local
+chains, so it cannot ingest channel history normally without that privileged
+intent.
+
+Invite the application with these OAuth2 scopes:
+
+| Scope | Why Crabstero uses it |
+|-------|------------------------|
+| `bot` | Add the bot user to the selected server. |
+| `applications.commands` | Install the `/pingme` and `/forgetme` slash commands. |
+
+Recommended bot permissions:
+
+| Permission | Why Crabstero uses it |
+|------------|------------------------|
+| View Channels | See the channels it should learn from and reply in. |
+| Send Messages | Send generated replies when mentioned. |
+| Send Messages in Threads | Reply when mentioned inside threads. |
+| Embed Links | Send occasional generated embed replies. |
+| Read Message History | Ingest accessible channel history on startup. |
+| Use External Emojis | Preserve learned custom emoji tokens in generated replies. |
+
+The combined permissions integer for the recommended set is
+`274878254080`.
+
+Example self-hosted invite URL:
+
+```text
+https://discord.com/oauth2/authorize?client_id=YOUR_CLIENT_ID&scope=bot%20applications.commands&permissions=274878254080
+```
+
+Replace `YOUR_CLIENT_ID` with the application ID from the Discord Developer
+Portal. Channel permission overwrites still apply, so you can limit where
+Crabstero learns and replies by restricting the bot role per channel.
+
+## Installation
+
+Create a directory for Crabstero, create a Python 3.14 virtual environment, and
+install the package from the project's Gitea package index:
+
+```bash
+mkdir crabstero && cd crabstero
+uv venv --python 3.14
+uv pip install crabstero \
+  --index https://git.logal.dev/api/packages/LogalDeveloper/pypi/simple/ \
+  --default-index https://pypi.org/simple
+```
+
+## Usage
+
+Run Crabstero with a Discord bot token from the environment:
+
+```bash
+TOKEN="your-discord-bot-token" uv run crabstero --database-path crabstero.db
+```
+
+On startup, Crabstero opens or creates the configured SQLite database, connects
+to Discord, and begins ingesting channel history and new messages it can read.
+Mention the bot in a channel to receive a generated reply once enough channel
+data has been collected.
+
+## Configuration
+
+Crabstero is configured through CLI flags, environment variables, and systemd
+credentials. CLI flags take precedence over environment defaults where both are
+available.
+
+| Setting | CLI flag | Environment variable | Fallback/default | Description |
+|---------|----------|----------------------|------------------|-------------|
+| Discord token | `--token` | `TOKEN` | systemd credential `token` | Required Discord bot token. |
+| Database path | `--database-path`, `--database` | `DATABASE_PATH` | `crabstero.db` | SQLite database file path. |
+| Ingest-only mode | `--ingest-only` | | disabled | Ingest history and real-time messages without replying. |
+| Metrics listener | `--listen-metrics` | `LISTEN_METRICS` | disabled | Prometheus metrics address, either `HOST:PORT` or `unix:/path.sock`. |
+| Metrics socket mode | `--metrics-unix-socket-mode` | `METRICS_UNIX_SOCKET_MODE` | unchanged | Octal file mode for Unix socket metrics listeners. |
+
+When running under systemd, Crabstero can read the bot token from a credential
+named `token`. It also sends readiness, stopping, and watchdog notifications
+when the relevant systemd environment variables are present.
+
+## Development
+
+Clone the Git repository and use [uv](https://docs.astral.sh/uv/) to sync the
+project environment from the lockfile:
+
+```bash
+git clone https://git.logal.dev/LogalDeveloper/Crabstero
+cd Crabstero
+uv sync --locked
+```
+
+The development toolchain uses [Ruff](https://docs.astral.sh/ruff/) for
+formatting and linting, [mypy](https://mypy.readthedocs.io/en/stable/) for type
+checking, [codespell](https://github.com/codespell-project/codespell) for typo
+detection, [pip-audit](https://github.com/pypa/pip-audit) for dependency
+auditing, and [pytest](https://docs.pytest.org/en/stable/) with
+[pytest-cov](https://pytest-cov.readthedocs.io/en/latest/) and
+[Coverage.py](https://coverage.readthedocs.io/) for tests and
+coverage reporting.
+
+Run the common checks:
+
+```bash
+uv run ruff format --check --diff .
+uv run ruff check .
+uv run mypy .
+uv run codespell
+uv run pip-audit --skip-editable
+uv run pytest
+```
+
+Run tests with coverage reporting:
+
+```bash
+uv run pytest -v --cov --cov-report=
+uv run coverage report
+```
+
+Tests are organized under `tests/unit` and `tests/integration`. The pytest
+configuration marks tests automatically based on those directories.
+
+## Links
+
+- Project page: <https://logal.dev/projects/crabstero/>
+- Source repository: <https://git.logal.dev/LogalDeveloper/Crabstero>
+
+## License
+
+Crabstero is licensed under the Apache License 2.0. See
+[LICENSE.txt](LICENSE.txt) for the full license text.