docs: add umbrella + journal READMEs

Root README orients new contributors on the build/upload/iterate
loop and points at ~/dev/CLAUDE.md for maubot patterns. journal/
README covers the three commands, the SQLite schema, known
quirks (edits don't re-trigger, subcommand detection scope), and
documents why this plugin uses @command.passive instead of the
more obvious @command.new.

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

README.md

@@ -0,0 +1,58 @@
+# maubot-plugins
+
+Umbrella for [maubot](https://github.com/maubot/maubot) plugins used by
+the aiolabs / Château du Faune Matrix stack. The maubot daemon itself
+is provisioned via `server-deploy/modules/services/maubot.nix` on the
+castle hosts; the actual plugin code lives here.
+
+## Plugins
+
+| Plugin | Purpose |
+|---|---|
+| [`journal/`](./journal/) | Farm-journal bot. `!journal <text>` records what you did, scoped per-user/room/timestamp. `!journal show [@user]` and `!journal today` query back. |
+
+## Building a plugin
+
+A `.mbp` is just a zip containing `maubot.yaml` + the plugin's Python
+modules at the root. No special tooling needed:
+
+```sh
+cd <plugin>/
+zip -j ../<plugin>.mbp maubot.yaml *.py
+```
+
+(`-j` strips the directory prefix so files land at the zip root.)
+
+## Uploading / iterating
+
+1. Open the maubot UI (e.g. `https://maubot.<domain>/_matrix/maubot/`).
+2. **Plugins → +** (first time) or click the existing plugin → upload
+   the new `.mbp`. Maubot keys plugins by `id`; uploading a new
+   `version` of the same `id` replaces the old one.
+3. **Hit Save** on the affected instance after upload — toggling
+   Enabled without Save will revert. Easy facepalm.
+
+Bump `version:` in `maubot.yaml` for every meaningful change so the
+maubot UI surfaces it cleanly and old `.mbp` files in
+`/var/lib/maubot/plugins/` aren't ambiguous.
+
+## Bot account convention
+
+Each plugin attaches to a Matrix client (a regular Matrix user account
+controlled by maubot). For the journal bot: `@journalbot:ariege.io`.
+Bot accounts are created the same way as any user — issue a
+registration token from the Continuwuity admin room
+(`!admin token issue --once`) and register through Element, then add
+the client in the maubot UI.
+
+Invite the bot to whichever rooms it should serve via `/invite
+@<bot>:<domain>` — maubot's autojoin handles new invites that arrive
+after the client's sync loop is up.
+
+## Patterns + gotchas
+
+Maubot-specific patterns (command decorators, multi-line caveats,
+`database_type` in `maubot.yaml`, etc.) live in `~/dev/CLAUDE.md`
+under "Maubot plugin development". Read that before writing a new
+plugin — there are several footguns that look fine but silently lose
+data.