feat(#2450): collapse the startup sweep into one inline DAG

The boot is now ONE DAG, assembled inline in submit_boot_tree — no boot_root
Noop anchor, no per-agent child DAGs, no display-only parent_id grouping: a
sweep MetaLock root (only when something is stale) that grows one rebuild
subgraph per stale agent into the same DAG (via append_subgraph, previous
commit), plus one Reconcile root per drifted agent (independent — a boot
reconcile needs no lock bump).

- submit_boot_tree builds the DagSpec inline; removed the single-use
  templates::{boot_root, startup_sweep} builders (inlined per the operator's
  "don't force single-use shapes into templates.rs" steer).
- fanout_specs simplified to the meta-update cascade path only — the startup
  sweep no longer fans out child DAGs, so its branch was dead.
- test: append_subgraph_roots_on_emitter_and_rebases_local_deps.

Vestigial after this (deliberately left as follow-ups, flagged in the PR):
NodeKind::Noop is now unconstructed (contained to hive-c0re, removable);
Template::StartupSweep is unconstructed but a hive-sh4re wire type
(frontend-coordinated removal).

hive-c0re/src/job_queue/scheduler.rs

@@ -17,7 +17,7 @@ use std::collections::HashMap;
 use std::sync::Arc;
 
 use super::exec::{self, NodeOutput};
-use super::{Claim, Source, Template, templates};
+use super::{Claim, Source, templates};
 use crate::coordinator::Coordinator;
 
 struct NodeDone {
@@ -166,26 +166,29 @@ async fn process_terminals(
     }
 }
 
-/// Child `Rebuild` specs for a completed `MetaLock` fan-out, grouped
-/// under the parent via `parent_id`. Meta-update children skip the
-/// per-agent relock (it would revert the bump the parent just
-/// committed); sweep children relock like a manual rebuild.
+/// Child `Rebuild` specs for a completed meta-update `MetaLock` fan-out,
+/// grouped under the parent via `parent_id`. Meta-update children skip the
+/// per-agent relock (`relock = false`) — it would revert the bump the parent
+/// just committed. This is now the meta-update cascade path only: the startup
+/// sweep no longer fans out child DAGs — it grows one rebuild subgraph per
+/// stale agent into its own DAG via `append_subgraph` (see
+/// `exec::run_meta_lock`).
 fn fanout_specs(claim: &Claim, agents: Vec<String>) -> Vec<super::DagSpec> {
-    let sweep = claim.template == Template::StartupSweep;
-    let (source, relock) = if sweep {
-        (Source::StartupSweep, true)
-    } else {
-        (Source::MetaUpdate, false)
-    };
-    let reason = if sweep {
-        "startup sweep".to_owned()
-    } else if let Some(approval_id) = claim.approval_id {
+    let reason = if let Some(approval_id) = claim.approval_id {
         format!("approval #{approval_id} meta input cascade")
     } else {
         "meta-update cascade".to_owned()
     };
     agents
         .into_iter()
-        .map(|agent| templates::rebuild(&agent, source, reason.clone(), Some(claim.dag_id), relock))
+        .map(|agent| {
+            templates::rebuild(
+                &agent,
+                Source::MetaUpdate,
+                reason.clone(),
+                Some(claim.dag_id),
+                false,
+            )
+        })
         .collect()
 }