Sign Markdown saved to the folder with the configured ENS name and key

README.md

@@ -1,11 +1,10 @@
 # Memona signature plugin
 
-Opens a WebDAV server as a folder inside Memona. It is the foundation for
-signing Markdown files with an ENS name as they are saved, writing `signer` and
-`signature` into each file's frontmatter so anyone can check who wrote it
-against the name's current ENSv2 records, using the
+Opens a WebDAV server as a folder inside Memona and signs every Markdown file
+saved to it with an ENS name, writing `signer` and `signature` into the file's
+frontmatter so anyone can check who wrote it against the name's current ENSv2
+records. Signing comes from the
 [md-ens-signature](https://github.com/capsulizers/md-ens-signature) library.
-This version is the WebDAV folder alone; signing is not in it yet.
 
 The plugin is a WASI component: it speaks no sockets of its own and makes every
 request through the host's HTTP interface, under the connection's permissions.
@@ -18,6 +17,9 @@ It registers one provider, `signature`, for the `signed-webdav` scheme.
 | Server address | The folder's address, for example `https://dav.example.com/files/` |
 | Username | Optional account name for HTTP basic authentication |
 | Password | Optional password, stored as a secret |
+| Signer name | The ENS name that signs, for example `laptop.alice.eth` |
+| Signing key | The private key of the address the name resolves to, stored as a secret |
+| Sepolia RPC address | The endpoint used to check signers against ENS, by default `https://ethereum-sepolia-rpc.publicnode.com` |
 
 Listing, reading, writing, creating directories, renaming and deleting behave
 as in the WebDAV plugin: reads and writes stream in pieces of at most 1 MiB,
@@ -25,6 +27,17 @@ conditional writes use `If-Match` and `If-None-Match`, change polling is not
 supported, a rename never replaces an existing target, and a folder with
 contents is refused rather than removed whole.
 
+## Signing
+
+Saving a `.md` file holds it whole, up to 8 MiB, and writes it once finished,
+with `signer` and `signature` set in its frontmatter; every other file streams
+straight through. The signature is EIP-191 `personal_sign` over the signer name
+and the body's SHA-256, made with the configured key; other frontmatter and the
+body stay byte for byte. A key that is not 32 bytes of hex refuses the
+connection, and a `.md` file that is not UTF-8 refuses the save. Reading passes
+every file through unchanged. The RPC address is for verifying signers, which a
+later version adds to reads.
+
 ## Building
 
 ```sh