feat(#2485): remove vestigial Noop + StartupSweep residuals

Since the boot sweep (#2450) and meta-update cascade (#2476) became
single DAGs that grow subgraphs in-place, nothing constructs the old
fan-out anchors/parents anymore:

- NodeKind::Noop (the old boot_root grouping anchor) — no constructors.
- Template::StartupSweep / Source::StartupSweep (the old fan-out parent
  template + cascade-child source) — replaced by Template::Boot and
  Source::AutoUpdate/MetaUpdate respectively.

Drops the three variants + their as_str arms + the Noop executor arm, and
refreshes the stale fan-out/anchor doc comments (Boot/MetaUpdate/Source
docs, coordinator.md, dashboard.md). Frontend: the queue-kind glyph moves
from the dead startup_sweep to boot (which had none), and the dead
rqe-source-startup_sweep style is dropped.

No behaviour change — pure dead-variant removal.

hive-c0re/src/job_queue/exec.rs

@@ -98,9 +98,6 @@ pub(super) async fn run_node(coord: &Arc<Coordinator>, claim: &Claim) -> Result<
         NodeKind::WriteDropin => run_write_dropin(coord, claim).await,
         NodeKind::WritePermFile => run_write_perm_file(coord, claim, &ctx).await,
         NodeKind::ApprovalDeploy => run_approval_deploy(coord, claim).await,
-        // A pure grouping anchor (boot root): no work, completes immediately so
-        // its child DAGs settle it and the boot tree resolves.
-        NodeKind::Noop => Ok(NodeOutput::default()),
         NodeKind::SetWanted { up } => run_set_wanted(coord, claim, *up),
     }
 }