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/workers/auto_update.rs

@@ -1,7 +1,7 @@
 //! Boot reconcile: on `hive-c0re serve` boot, (a) run the config path
-//! for agents whose per-agent rev marker is stale — a `StartupSweep`
-//! DAG (meta hyperhive lock bump) fanning out `Rebuild` children for
-//! the stale agents whose `wanted` power intent is `Up` — and (b)
+//! for agents whose per-agent rev marker is stale — one `Boot` DAG
+//! (meta hyperhive lock bump) that grows a `Rebuild` subgraph for each
+//! stale agent whose `wanted` power intent is `Up` — and (b)
 //! converge every other drifted agent to its persisted `wanted` via
 //! `Reconcile` DAGs. Two rules keep boot-time nix work minimal:
 //!
@@ -194,10 +194,10 @@ pub fn topology_sort(
 }
 
 /// Boot reconcile (see the module doc): classify every agent by rev
-/// freshness + persisted `wanted` intent, submit one `StartupSweep`
-/// DAG (hyperhive lock bump → fan-out rebuilds for stale wanted-up
-/// agents) when anything is stale, and `Reconcile` DAGs for agents
-/// whose observed power state drifted from `wanted`. Returns Ok even
+/// freshness + persisted `wanted` intent, submit one `Boot` DAG
+/// (hyperhive lock bump growing an in-DAG rebuild subgraph per stale
+/// wanted-up agent) when anything is stale, and `Reconcile` DAGs for
+/// agents whose observed power state drifted from `wanted`. Returns Ok even
 /// if some submissions failed.
 pub async fn run(coord: Arc<Coordinator>) -> Result<()> {
     let containers = match lifecycle::list().await {
@@ -287,8 +287,8 @@ pub async fn run(coord: Arc<Coordinator>) -> Result<()> {
     Ok(())
 }
 
-/// Submit this boot's work as **one DAG** (no `boot_root` Noop anchor, no
-/// per-agent child DAGs). Node 0 is the sweep `MetaLock` (only when
+/// Submit this boot's work as **one DAG** (no anchor node, no per-agent
+/// child DAGs). Node 0 is the sweep `MetaLock` (only when
 /// something is stale) — its executor bumps the hyperhive lock, then grows
 /// one rebuild subgraph per stale agent into *this same* DAG (rooted on the
 /// `MetaLock`, so they build against the post-bump lock; see