fix(ci): unblock nix flake check after clippy 0.1.95 bump (#1368)

The nixpkgs bump to clippy 0.1.95 / cargo 1.95.0 added + strengthened a
large batch of lints. CI denied ALL warnings (`-D warnings`) against the
`pedantic = warn` workspace lint, so the bump hard-failed `nix flake
check` workspace-wide with zero code changes — and would recur on every
future clippy bump.

Posture fix (the durable part): CI now runs
`-D warnings -A clippy::pedantic`, so the default/correctness/style lints
stay a hard gate while the "extra, opinionated" pedantic group is
advisory only (still `warn` for local `cargo clippy` via the workspace
lints table, just non-blocking in CI). `-A` rather than `-W` so the
group drop doesn't re-enable the specific pedantic lints the workspace
allows (e.g. `must_use_candidate`).

Also fixes the genuine DEFAULT/STYLE lints the bump surfaced across the
workspace (doc_lazy_continuation, collapsible_if, ptr_arg,
match_like_matches_macro, …) via `cargo clippy --fix` + manual stragglers
(`too_many_arguments` #[allow] on the host-config constructors), and
three tests that had rotted while the CI runner was offline (#1221):
- topology::top_level_agents_in_multi_root — hardcoded unsorted expected
- rebuild_queue::depends_on_evicted_dep_counts_as_resolved — needs
  MAX_HISTORY_PER_KIND newer terminals to evict, not one
- coordinator::agent_paths doctest — illustrative pseudo-code, now `ignore`

Validated: clippy + formatting + cargo-test checks all pass.

hive-matrix-mcp/src/handlers.rs

@@ -450,8 +450,8 @@ pub async fn collect_unread(client: &Client) -> Vec<crate::protocol::RoomUnread>
     use crate::protocol::RoomUnread;
     let mut result = Vec::new();
     for room in client.joined_rooms() {
-        let count = u32::try_from(room.unread_notification_counts().notification_count)
-            .unwrap_or(u32::MAX);
+        let count =
+            u32::try_from(room.unread_notification_counts().notification_count).unwrap_or(u32::MAX);
         if count == 0 {
             continue;
         }