/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/collab/src/db/queries/projects.rs

@@ -728,6 +728,11 @@ impl Database {
                         is_ignored: db_entry.is_ignored,
                         is_external: db_entry.is_external,
                         git_status: db_entry.git_status.map(|status| status as i32),
+                        // This is only used in the summarization backlog, so if it's None,
+                        // that just means we won't be able to detect when to resummarize
+                        // based on total number of backlogged bytes - instead, we'd go
+                        // on number of files only. That shouldn't be a huge deal in practice.
+                        size: None,
                         is_fifo: db_entry.is_fifo,
                     });
                 }