/auto (#16696)

Add `/auto` behind a feature flag that's disabled for now, even for
staff.

We've decided on a different design for context inference, but there are
parts of /auto that will be useful for that, so we want them in the code
base even if they're unused for now.

Release Notes:

- N/A

---------

Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

crates/worktree/src/worktree.rs

@@ -3227,6 +3227,8 @@ pub struct Entry {
     pub git_status: Option<GitFileStatus>,
     /// Whether this entry is considered to be a `.env` file.
     pub is_private: bool,
+    /// The entry's size on disk, in bytes.
+    pub size: u64,
     pub char_bag: CharBag,
     pub is_fifo: bool,
 }
@@ -3282,6 +3284,7 @@ impl Entry {
             path,
             inode: metadata.inode,
             mtime: Some(metadata.mtime),
+            size: metadata.len,
             canonical_path,
             is_symlink: metadata.is_symlink,
             is_ignored: false,
@@ -5210,6 +5213,7 @@ impl<'a> From<&'a Entry> for proto::Entry {
             is_external: entry.is_external,
             git_status: entry.git_status.map(git_status_to_proto),
             is_fifo: entry.is_fifo,
+            size: Some(entry.size),
         }
     }
 }
@@ -5231,6 +5235,7 @@ impl<'a> TryFrom<(&'a CharBag, proto::Entry)> for Entry {
             path,
             inode: entry.inode,
             mtime: entry.mtime.map(|time| time.into()),
+            size: entry.size.unwrap_or(0),
             canonical_path: None,
             is_ignored: entry.is_ignored,
             is_external: entry.is_external,