clippy: fix lints that crane's cargoClippy properly enforces (#538)

The naersk → crane swap in the parent commit flips clippy from
silently passing to actually failing on `-D warnings` (naersk's
`mode = "clippy"` mangled the `--` separator so the deny never took
effect). This commit clears the surfaced lints so the workspace
builds clean under the new enforcement — every fix is mechanical and
preserves behaviour. Tests still pass (160 across the workspace).

Auto-fixes via `cargo clippy --fix`:
- `doc_markdown` (19 sites): bare identifiers in doc comments
  wrapped in backticks
- `format_in_format_args`, `explicit_into_iter_loop`,
  `redundant_closure_for_method_calls`, `useless_conversion`, and
  a few more — mechanical rewrites of the kind cargo can apply
  safely.

Hand-fixed:
- `match_same_arms` (forge_notify::is_atx_heading): two arms returning
  `true` collapsed into a single `matches!` pattern.
- `cast_sign_loss` + `format_push_string` (mcp.rs status formatter):
  guarded `i64 → u64` through `u64::try_from(…).unwrap_or(0)` (status
  timestamps are always positive in practice; clamp the skew edge to
  0) and swapped `out.push_str(&format!(…))` for `write!` into the
  buffer with an infallible-writer `let _ =`.
- `doc_lazy_continuation` in turn.rs + manager_server.rs + sh4re/lib.rs:
  doc paragraphs that the markdown parser was treating as list-item
  continuations got either a separating blank line or a `/`-for-`+`
  word swap so the parser stops seeing a list.
- `unused_async` (manager_server::handle_request_schedule_prompt):
  function has no `.await`; dropped the `async` and its `.await` call
  site.
- `needless_pass_by_value` (scheduled_prompts::submit): take
  `&NewSchedule` instead of moving the struct in; updated two prod
  callers and eight test sites to pass references.
- `type_complexity` (approvals::mark_cancelled): hoisted the
  7-tuple SELECT row shape into a `type CancelLookupRow = (…);` alias.

Allow-with-reason for intentional patterns:
- `option_option` (6 sites across dashboard / scheduled_prompts /
  manager_server): `Option<Option<T>>` carries three-state PATCH
  semantics (missing key = leave alone, `Some(None)` = clear,
  `Some(Some(v))` = set). Collapsing to `Option<T>` loses the
  "clear" state.
- `dead_code` (rebuild_queue::QueueKind::Destroy /
  QueueSource::CrashRecover; topology::parent_of / default_seed):
  wire-shape variants + API surfaces kept for the upcoming features
  (#361 follow-ups, future `Destroy` queue routing, crash-recovery
  path). Allowed at the variant / function level with the rationale
  in `reason = "…"`.
- `too_many_lines` on three specific call-sites: a 117-line
  exhaustive-variant test (dashboard_events::kind_tag_matches_…),
  the meta-flake string template renderer
  (meta::render_flake_with_lookup), and the notification poll loop
  (forge_notify::poll_once) — splitting any of them would just hide
  the contiguous shape they exist to keep visible.

`nix flake check` formatting target is still broken on main itself
(pre-existing nixfmt drift across ~28 files unrelated to this PR);
left alone here so the scope stays "crane port + lints the port
exposed" and the operator's review doesn't have to triage drive-by
nixfmt churn.

hive-c0re/src/crash_watch.rs

@@ -139,6 +139,46 @@ fn is_deliberate_stop(
     active.is_some_and(is_op_kind) || recently_cleared.is_some_and(is_op_kind)
 }
 
+fn emit_login_transitions(
+    coord: &Coordinator,
+    prev: &HashSet<String>,
+    current: &HashSet<String>,
+    sub_agents: &[String],
+    prev_sub_agents: &HashSet<String>,
+) {
+    for agent in current.difference(prev) {
+        tracing::info!(%agent, "agent logged in");
+        coord.notify_manager(&hive_sh4re::HelperEvent::LoggedIn {
+            agent: agent.clone(),
+        });
+    }
+    // Detect transitions into "needs login": an agent that was previously
+    // logged-in goes unsigned (credentials deleted), OR a brand-new agent
+    // appears without a session.
+    //
+    // prev_needs uses prev_sub_agents (the agent set from the last tick) so
+    // that a newly-spawned agent — which does not appear in prev_sub_agents —
+    // is absent from prev_needs even though it's not in prev_logged_in.
+    // Without this, new agents land in both prev_needs and current_needs and
+    // the set difference is empty, silently dropping the event.
+    let prev_needs: HashSet<&str> = prev_sub_agents
+        .iter()
+        .map(String::as_str)
+        .filter(|n| !prev.contains(*n))
+        .collect();
+    let current_needs: HashSet<&str> = sub_agents
+        .iter()
+        .map(String::as_str)
+        .filter(|n| !current.contains(*n))
+        .collect();
+    for agent in current_needs.difference(&prev_needs) {
+        tracing::info!(%agent, "agent needs login");
+        coord.notify_manager(&hive_sh4re::HelperEvent::NeedsLogin {
+            agent: (*agent).to_owned(),
+        });
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -186,44 +226,3 @@ mod tests {
         }
     }
 }
-
-fn emit_login_transitions(
-    coord: &Coordinator,
-    prev: &HashSet<String>,
-    current: &HashSet<String>,
-    sub_agents: &[String],
-    prev_sub_agents: &HashSet<String>,
-) {
-    for agent in current.difference(prev) {
-        tracing::info!(%agent, "agent logged in");
-        coord.notify_manager(&hive_sh4re::HelperEvent::LoggedIn {
-            agent: agent.clone(),
-        });
-    }
-    // Detect transitions into "needs login": an agent that was previously
-    // logged-in goes unsigned (credentials deleted), OR a brand-new agent
-    // appears without a session.
-    //
-    // prev_needs uses prev_sub_agents (the agent set from the last tick) so
-    // that a newly-spawned agent — which does not appear in prev_sub_agents —
-    // is absent from prev_needs even though it's not in prev_logged_in.
-    // Without this, new agents land in both prev_needs and current_needs and
-    // the set difference is empty, silently dropping the event.
-    let prev_needs: HashSet<&str> = prev_sub_agents
-        .iter()
-        .map(String::as_str)
-        .filter(|n| !prev.contains(*n))
-        .collect();
-    let current_needs: HashSet<&str> = sub_agents
-        .iter()
-        .map(String::as_str)
-        .filter(|n| !current.contains(*n))
-        .collect();
-    for agent in current_needs.difference(&prev_needs) {
-        tracing::info!(%agent, "agent needs login");
-        coord.notify_manager(&hive_sh4re::HelperEvent::NeedsLogin {
-            agent: (*agent).to_owned(),
-        });
-    }
-}
-