Docs: refresh diffs plugin docs

extensions/diffs/README.md

@@ -60,11 +60,20 @@ Useful options:
 - `fileMaxWidth`: max width override in CSS pixels (`640`-`2400`)
 - `expandUnchanged`: expand unchanged sections (per-call option only, not a plugin default key)
 - `path`: display name for before and after input
+- `lang`: language hint for before/after input; unknown values fall back to plain text
 - `title`: explicit viewer title
-- `ttlSeconds`: artifact lifetime
+- `ttlSeconds`: artifact lifetime for viewer and standalone file outputs
 - `baseUrl`: override the gateway base URL used in the returned viewer link (origin or origin+base path only; no query/hash)
 - `viewerBaseUrl` plugin config: persistent fallback used when a tool call omits `baseUrl`
 
+Legacy input aliases still accepted for backward compatibility:
+
+- `format` -> `fileFormat`
+- `imageFormat` -> `fileFormat`
+- `imageQuality` -> `fileQuality`
+- `imageScale` -> `fileScale`
+- `imageMaxWidth` -> `fileMaxWidth`
+
 Input safety limits:
 
 - `before` and `after`: max 512 KiB each