Import type names instead of writing their paths (#355)

The style guide imports types and uses them unqualified. 222 places
wrote a path such as std::collections::HashMap or std::time::Duration
inline; each file now imports the type once, one use a module, and
names it bare. Done with a script, file by file, only where the name is
unambiguous there:
- one path for the name throughout the file, and not a name the file
  already binds otherwise (its own types, other imports, a function's
  local use);
- not a name generic enough to mislead bare (Error, Result, Value,
  Mutex, Client, Request, Response, Command, Event, Context, Map, Ok);
- only code a normal build compiles, so no import is unused outside
  tests or names a crate only tests depend on.

193 paths stay, those cases above. No behaviour change.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/feed/src/guard.rs

@@ -14,6 +14,7 @@ use std::sync::Arc;
 use std::task::{Context, Poll};
 
 use anyhow::{Context as _, Result};
+use http::Extensions;
 use hyper_util::client::legacy::connect::{Connection, HttpInfo};
 
 type BoxError = Box<dyn std::error::Error + Send + Sync>;
@@ -153,7 +154,7 @@ where
         let allowed = self.allowed.clone();
         Box::pin(async move {
             let conn = connecting.await.map_err(Into::into)?;
-            let mut extras = http::Extensions::new();
+            let mut extras = Extensions::new();
             conn.connected().get_extras(&mut extras);
             // Refused when the peer is unknown too: a connection this cannot check is one it
             // cannot vouch for.