dashboard: show and edit per-agent resource limits in core LOAD tab

Adds CPU/memory cap columns and an inline edit form to the container-load
table in /core.html, backed by a new POST /api/resource-limits/{name}
dashboard endpoint.

## Backend (hive-c0re)

lifecycle_ops.rs — new post_resource_limits handler:
- Parses ResourceLimitsForm { cpu_quota, memory_max } (both optional; empty
  string = clear override, fall back to hive-wide default).
- Validates each non-empty value via resource_limits::validate_cpu_quota /
  validate_memory_max — returns 422 UNPROCESSABLE_ENTITY with a human-
  readable message on invalid input so the dashboard can surface it inline.
- Calls meta::commit_resource_limits (staged git write under META_LOCK, same
  as hivectl set-limits).
- Re-applies the drop-in immediately via lifecycle::write_dropins so the new
  ceilings take effect on the next container start without waiting for a
  rebuild.
- Triggers rescan_containers_and_emit so ContainerView.cpu_quota/memory_max
  update via SSE without waiting for the next periodic sweep.

dashboard/mod.rs — registers the route:
  POST /api/resource-limits/{name}

## Frontend (core.js + system-sections.css)

core.js:
- containersState derived from /api/state snapshot alongside tombstonesState
  — supplies configured cpu_quota/memory_max to the LOAD table.
- lastLoadRows stash lets SSE-triggered re-renders call renderContainerLoad
  without waiting for the next 5s poll.
- renderContainerLoad: adds cpu cap / mem cap columns (muted; tooltip
  'configured ceiling — takes effect on next start') sourced from
  ContainerView, plus a per-row S3T toggle button that expands an inline
  edit form with cpu_quota / memory_max text inputs and a S4V3 button.
  The edit form shows a restart hint, surfaces validation errors inline, and
  collapses on success.
- container_state_changed SSE handler: updates containersState in place and
  re-renders the LOAD table so the cap columns flip immediately after a save.

system-sections.css:
- CSS for the new cap columns (.cload-cap-th, .cload-cap) and inline edit
  form (.cload-edit-row, .cload-edit-form, .cload-edit-label, etc.).
- Remove dead .rqe-step rule (step sub-step label retired from the wire in
  'job_queue: retire the now-off-wire step sub-step label').

frontend/packages/dashboard/src/system-sections.css

@@ -213,12 +213,6 @@
 .rqe-node-arrow { color: var(--muted); }
 .rqe-node-log { margin-left: 0.1em; text-decoration: none; }
 
-.rqe-step {
-  flex-basis: 100%;
-  margin: 0.1em 0 0 1.8em;
-  color: var(--cyan);
-  font-size: 0.85em;
-}
 .rqe-error {
   flex-basis: 100%;
   margin: 0.3em 0 0;
@@ -355,6 +349,61 @@
   background: var(--red);
 }
 
+/* Configured-cap columns: muted header so they read apart from live metrics.
+   The S3T button sits in its own column; keep it compact. */
+.cload-cap-th {
+  color: var(--muted);
+}
+.cload-cap {
+  color: var(--muted);
+}
+.cload-set-btn {
+  padding: 0.1em 0.5em;
+  font-size: 0.8em;
+}
+
+/* Inline edit row — spans all columns, contains a mini-form. */
+.cload-edit-row td {
+  border-top: none;
+  padding-top: 0;
+}
+.cload-edit-cell {
+  padding: 0.2em 0.4em 0.6em 1.2em;
+}
+.cload-edit-form {
+  display: flex;
+  flex-wrap: wrap;
+  align-items: center;
+  gap: 0.5em;
+}
+.cload-edit-label {
+  display: flex;
+  align-items: center;
+  gap: 0.3em;
+  font-size: 0.85em;
+  color: var(--muted);
+}
+.cload-cpu-input,
+.cload-mem-input {
+  width: 7em;
+  font-size: 0.9em;
+}
+.cload-save-btn {
+  padding: 0.15em 0.6em;
+  font-size: 0.85em;
+}
+.cload-edit-hint {
+  font-size: 0.8em;
+}
+.cload-edit-err {
+  color: var(--red);
+  font-size: 0.85em;
+}
+
+/* Remove the now-dead `.rqe-step` rule (the `step` sub-step label was
+   retired from the wire in `feat(job_queue): retire the now-off-wire step
+   sub-step label` — the rule has had no JS referents since then). */
+
 /* ─── K3PT ST4T3 › stale permission entries sub-section ────────────────────
    Agents with explicit capability / tool-group entries in the JSON but no
    live container (renamed or manually-deleted agents). Lazy-loaded on tab