hive-c0re: split OpenAPI summary/description, move param docs to params

utoipa splits a handler's doc comment on the first blank `///` line:
everything before it becomes the OpenAPI `summary` (shown in Swagger
UI's collapsed endpoint-list row), everything after becomes the
`description` (only shown once that row is expanded). With no blank
line, the whole doc comment becomes the summary and the description is
empty — which is what every handler in hive-c0re/src/dashboard/ was
doing, so the all-endpoints list showed full multi-sentence prose next
to every route instead of a short one-liner.

For every `#[utoipa::path(...)]`-annotated handler across the 19 files
in that module:

- Inserted a blank `///` line after the first short sentence/clause so
  utoipa's split produces a real summary + description, where the doc
  comment had more to say. Left already-short single-clause docs alone
  (nothing to split).
- Where a query struct derives `IntoParams`, moved param prose that
  duplicated a field's own doc comment out of the handler doc (the
  field already documents itself in the generated spec), or added a
  field doc where the handler explained a param that had none.

No behavior changes — doc comments and `params()` description text
only. Verified `cargo build -p hive-c0re` (clean) and `nix fmt` (zero
changes) after.

Closes #2969

hive-c0re/src/dashboard/state_files.rs

@@ -18,6 +18,9 @@ use crate::paths::{AGENTS_ROOT, SHARED_ROOT};
 
 #[derive(Deserialize, IntoParams)]
 pub(super) struct StateFileQuery {
+    /// Absolute path under an agent's `state/` dir or under `shared/`;
+    /// checked against the allow-list (`docs/security.md::State-file
+    /// endpoint`).
     path: String,
 }
 
@@ -164,10 +167,10 @@ pub fn scan_validated_paths(body: &str) -> Vec<String> {
     out
 }
 
-/// `GET /api/state-file?path=…` — serve an allow-listed per-agent
-/// `state/` or `shared/` file. Raster images get their real
-/// content-type; everything else is served as (possibly truncated)
-/// text.
+/// `GET /api/state-file?path=…` — serve an allow-listed file.
+///
+/// Raster images get their real content-type; everything else is
+/// served as (possibly truncated) text.
 #[utoipa::path(
     get,
     path = "/api/state-file",