Doc comments on ipx-feed's and ipx-directory's public items (#354)

The style guide asks for doc comments on a library's public API. Every
type, function, constant and static the two libraries export now has
one, saying what it is for or what it does that its name does not:
fetch follows redirects itself so credentials stay on the feed's host,
Config::parse refuses repeated token names, Store::due_one is the
admin's Refresh. Fields and variants whose names say it all have none,
as the guide allows.

category_path's comment had slid above categories(), which then had
two; each has its own again.

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

crates/directory/src/lib.rs

@@ -63,7 +63,9 @@ pub struct Item {
     pub guid: String,
     pub title: Option<String>,
     pub link: Option<String>,
+    /// Unix seconds.
     pub published: Option<i64>,
+    /// Seconds.
     pub duration: Option<i64>,
     /// As the feed sent it, unsanitized.
     pub description: Option<String>,
@@ -80,6 +82,7 @@ pub struct SnapshotEntry {
     pub category: Option<String>,
 }
 
+/// What became of a snapshot's entries.
 #[derive(Debug, Clone, Default, Serialize, Deserialize, PartialEq)]
 pub struct SnapshotResult {
     pub accepted: usize,
@@ -91,6 +94,7 @@ pub struct SnapshotResult {
     pub refused_invalid: usize,
 }
 
+/// Who a token belongs to and what it may do: `/v1/me`'s answer.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Me {
     pub name: String,
@@ -105,11 +109,13 @@ pub struct Instance {
     pub subscribers: i64,
 }
 
+/// A feed an admin removed from the directory, which snapshots may not bring back.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Blocked {
     pub id: String,
     pub url: Option<String>,
     pub title: Option<String>,
+    /// When it was blocked, Unix seconds.
     pub at: i64,
 }
 
@@ -121,6 +127,8 @@ pub const MAX_SNAPSHOT: usize = 20_000;
 /// to a feed fetches it itself anyway: every six hours was 3.9 GB of feeds a day (#243).
 pub const REFRESH_EVERY: i64 = 12 * 3600;
 
+/// The running directory: its database, the tokens it accepts and the client its refresher
+/// fetches feeds with.
 pub struct Directory {
     pub store: Store,
     tokens: RwLock<Vec<Token>>,
@@ -134,9 +142,12 @@ pub struct Directory {
 /// How long the public pages show the same copy of the list.
 const PAGES_LIST_FOR: Duration = Duration::from_secs(60);
 
+/// The directory as every handler and task holds it.
 pub type Shared = Arc<Directory>;
 
 impl Directory {
+    /// A directory on `store`, accepting `tokens`, whose refresher may reach the internal
+    /// addresses `fetch_internal` lists and no others.
     pub fn new(
         store: Store,
         tokens: Vec<Token>,
@@ -288,6 +299,7 @@ pub async fn reloader(dir: Shared, path: std::path::PathBuf) {
     }
 }
 
+/// Every route: the API under `/v1`, behind a token, and the public pages.
 pub fn router(dir: Shared) -> Router {
     let v1 = Router::new()
         .route("/v1/me", get(me))