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/directory/src/otel.rs

@@ -2,6 +2,8 @@
 //! caller and out to a callee, so one trace follows a request from the browser through ipx-web
 //! and ipx into the directory.
 
+use axum::http::HeaderMap;
+
 /// Traces over OTLP, to Tempo for one, when OTEL_EXPORTER_OTLP_ENDPOINT names a collector
 /// (`http://host:4318`: the exporter speaks OTLP over HTTP and adds `/v1/traces`). The exporter
 /// reads that and the other `OTEL_` variables itself.
@@ -24,7 +26,7 @@ pub fn provider(service: &'static str) -> anyhow::Result<Option<opentelemetry_sd
 /// header can be set: a position saved by sendBeacon, and the playlist Safari's player fetches
 /// itself (#192).
 #[must_use]
-pub fn remote_parent(headers: &axum::http::HeaderMap, query: Option<&str>) -> Option<opentelemetry::Context> {
+pub fn remote_parent(headers: &HeaderMap, query: Option<&str>) -> Option<opentelemetry::Context> {
     use opentelemetry::trace::{SpanContext, SpanId, TraceContextExt, TraceFlags, TraceId, TraceState};
     let v = match headers.get("traceparent") {
         Some(h) => h.to_str().ok()?,