assistant: Add basic glob support for expanding items in /docs (#14370)

This PR updates the `/docs` slash command with basic globbing support
for expanding docs.

A `*` can be added to the item path to signify the end of a prefix
match.

For example:

```
# This will match any documentation items starting with `auk::`.
# In this case, it will pull in the docs for each item in the crate.
/docs docs-rs auk::*

# This will match any documentation items starting with `auk::visitor::`,
# which will pull in docs for the `visitor` module.
/docs docs-rs auk::visitor::*
```


https://github.com/user-attachments/assets/5e1e21f1-241b-483f-9cd1-facc3aa76365

Release Notes:

- N/A

crates/indexed_docs/src/store.rs

@@ -103,6 +103,15 @@ impl IndexedDocsStore {
             .await
     }
 
+    pub async fn load_many_by_prefix(&self, prefix: String) -> Result<Vec<(String, MarkdownDocs)>> {
+        self.database_future
+            .clone()
+            .await
+            .map_err(|err| anyhow!(err))?
+            .load_many_by_prefix(prefix)
+            .await
+    }
+
     pub fn index(
         self: Arc<Self>,
         package: PackageName,
@@ -257,6 +266,28 @@ impl IndexedDocsDatabase {
         })
     }
 
+    pub fn load_many_by_prefix(&self, prefix: String) -> Task<Result<Vec<(String, MarkdownDocs)>>> {
+        let env = self.env.clone();
+        let entries = self.entries;
+
+        self.executor.spawn(async move {
+            let txn = env.read_txn()?;
+            let results = entries
+                .iter(&txn)?
+                .filter_map(|entry| {
+                    let (key, value) = entry.ok()?;
+                    if key.starts_with(&prefix) {
+                        Some((key, value))
+                    } else {
+                        None
+                    }
+                })
+                .collect::<Vec<_>>();
+
+            Ok(results)
+        })
+    }
+
     pub fn insert(&self, key: String, docs: String) -> Task<Result<()>> {
         let env = self.env.clone();
         let entries = self.entries;