Type is_shared and say who the flag counts

stat() and readdir() return FSItemRead, so the is_shared the docs lead
with typechecks for TypeScript consumers rather than erroring on FSItem.

The docs said "you have shared", but the query has no issuer predicate:
a manage delegate's re-share sets the owner's flag too, which is the
useful answer and matches getShares().

src/docs/src/FS/readdir.md

@@ -41,7 +41,7 @@ An object with the following properties:
 
 A `Promise` that resolves to an array of [`FSItem`](/Objects/fsitem/) objects (files and directories) within the specified directory.
 
-Each item carries `is_shared`: `true` when you have shared it with someone, `false` when you have not, and `null` for items that are not yours. Only shares on the item itself count — the children of a folder you shared report `false`, since the share lives on the folder. Use [`getShares()`](/FS/getShares/) on an item to see who can reach it, including access inherited from a parent.
+Each item carries `is_shared`: `true` when it has been shared with someone, `false` when it has not, and `null` for items that are not yours. Only shares on the item itself count — the children of a folder you shared report `false`, since the share lives on the folder. Use [`getShares()`](/FS/getShares/) on an item to see who can reach it, including access inherited from a parent.
 
 When the request includes `cursor` (even `null`) or `includeTotal`, the promise instead resolves to a page object:
 

src/docs/src/FS/stat.md

@@ -37,7 +37,7 @@ An object with the following properties:
 
 A `Promise` that resolves to the [`FSItem`](/Objects/fsitem) object of the specified file or directory.
 
-The item carries `is_shared`: `true` when you have shared it with someone, `false` when you have not, and `null` when the item is not yours — whether someone else's file has other recipients is not yours to see. Only shares **on the item itself** count. A file inside a folder you shared is reachable through that folder without being shared itself, so it reports `false`; [`getShares()`](/FS/getShares/) is what reports inherited access.
+The item carries `is_shared`: `true` when it has been shared with someone, `false` when it has not, and `null` when the item is not yours — whether someone else's file has other recipients is not yours to see. It covers shares granted by anyone holding `manage` on the item, not only your own, the same way [`getShares()`](/FS/getShares/) does. Only shares **on the item itself** count. A file inside a folder you shared is reachable through that folder without being shared itself, so it reports `false`; `getShares()` is what reports inherited access.
 
 With `returnShares: true`, the result also carries `shares` — an array of the same share objects [`getShares()`](/FS/getShares/) returns, including access inherited from a parent folder and unclaimed invitations. It is empty unless you own the item or hold `manage` on it, so asking for it never fails a `stat()` you were otherwise allowed to make.
 

src/docs/src/Objects/fsitem.md

@@ -42,7 +42,7 @@ An integer containing the size of the item in bytes. If the item is a directory,
 
 #### `is_shared` (Boolean | null)
 
-Whether you have shared this item with anyone: `true` if you have, `false` if you have not, and `null` when the item is not yours. Only shares on the item itself count, not access inherited from a shared parent folder. Set by [`stat()`](/FS/stat/) and [`readdir()`](/FS/readdir/); absent on items obtained any other way.
+Whether this item has been shared with anyone: `true` if it has, `false` if it has not, and `null` when the item is not yours. Counts shares granted by anyone holding `manage` on it, and only shares on the item itself — not access inherited from a shared parent folder. Set by [`stat()`](/FS/stat/) and [`readdir()`](/FS/readdir/); absent on items obtained any other way.
 
 ## Methods