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/matrix_accounts.rs

@@ -104,7 +104,9 @@ fn account_name_from_filename(fname: &str) -> Option<String> {
 }
 
 /// `GET /api/matrix-accounts?agent=<name>` — matrix accounts provisioned
-/// for `agent`, backfilled with `homeserver`/`live`/`user_id` from the daemon's
+/// for `agent`.
+///
+/// Backfilled with `homeserver`/`live`/`user_id` from the daemon's
 /// snapshot.
 #[utoipa::path(
     get,
@@ -188,6 +190,7 @@ struct MatrixLoginResult {
 }
 
 /// Provision (or refresh) the token for an agent's extra matrix account.
+///
 /// password mode → `m.login.password`; token mode → validate via `whoami`.
 /// On success writes the token to `matrix-token-<account>` via hive-priv and
 /// kicks the daemon. Operator-authenticated (dashboard). Never echoes the
@@ -293,7 +296,9 @@ struct GithubAccountResult {
 }
 
 /// Provision (or refresh) an agent's GitHub PAT from the dashboard
-/// credentials tab. Validates the agent name, then writes the PAT to
+/// credentials tab.
+///
+/// Validates the agent name, then writes the PAT to
 /// `<state>/github-token` (`0600`, agent-owned) via hive-priv. No account
 /// creation and no daemon to kick — the agent's `gh` wrapper / git credential
 /// helper read the file live, so the new token takes effect immediately.
@@ -339,9 +344,10 @@ struct GithubAccountStatus {
 }
 
 /// `GET /api/github-account?agent=<name>` — whether the agent has a GitHub
-/// PAT provisioned (its `github-token` file exists). Lets the credentials tab
-/// show "token stored" vs "not set" instead of a black-hole paste field.
-/// Never returns the token itself.
+/// PAT provisioned (its `github-token` file exists).
+///
+/// Lets the credentials tab show "token stored" vs "not set" instead of a
+/// black-hole paste field. Never returns the token itself.
 #[utoipa::path(
     get,
     path = "/api/github-account",