feat: per-agent CPU and memory limits

The hive applies one `agentCpuQuota` / `agentMemoryMax` to every
container. That's the right default and the wrong ceiling: a build-heavy
agent needs headroom the other twelve don't, and raising the hive-wide
value to suit it hands that headroom to everyone.

Adds a per-agent override, persisted host-side and resolved per-field
against the hive defaults.

Follows the existing `meta/*.json` pattern (`capabilities.json`,
`tool-groups.json`): a host-side map read by `hive-c0re`, staged and
committed in the meta repo so every change lands in the audit trail.

```json
{ "sock": { "cpu_quota": "400%", "memory_max": "8G" } }
```

Fallback is **per field**, not per agent: an entry with only
`memory_max` leaves that agent on the hive-wide CPU quota. Absent file,
absent agent and absent field all resolve to the hive default, so the
feature is inert until someone opts an agent in.

Unlike the other meta files this one is **not** injected into the
container — a limit is something done *to* an agent, not something it
reads about itself.

```
hivectl agents set-limits sock --cpu-quota 400% --memory-max 8G
hivectl agents set-limits sock --reset
```

Values are validated before they're persisted: they go into a systemd
drop-in verbatim, and a typo there makes the unit fail to *start* —
turning a fat-fingered quota into a container that won't come back.

The command is declarative: each call replaces the agent's whole entry.
That makes a forgotten flag a silent revert, so a bare `set-limits
<name>` is rejected at the clap layer and clearing needs an explicit
`--reset`.

`ContainerView` gains `cpu_quota` / `memory_max`, both always populated:
there's no "unset" state to render, only "same as everyone else". They
reflect what the drop-in *says* — what the next start will enforce — not
a live cgroup reading.

The write goes through `meta::commit_resource_limits` rather than the
bare setter, so it's staged and committed under `META_LOCK`. Writing
without committing would leave the meta working tree dirty for the next
`prepare_deploy` to trip over.

Docs: `persistence.md` (the new meta file, and why it isn't injected),
`tools/hivectl.md` (the prose guide), `tools/hivectl-cli.md`
(regenerated clap dump).

Closes: internal/requests issue 25

docs/tools/hivectl.md

@@ -178,6 +178,34 @@ resume drains the backlog rather than dropping it. Points worth knowing:
 - Visible as ` paused` in `agents list`'s STATUS column, as a `paused`
   field on the JSON rows, and as a badge on the dashboard card.
 
+### Per-agent resource limits
+
+```bash
+hivectl agents set-limits sock --cpu-quota 400% --memory-max 8G
+hivectl agents set-limits sock --memory-max 8G    # CPU falls back to the hive default
+hivectl agents set-limits sock --reset            # drop all overrides
+```
+
+Overrides the hive-wide `services.hyperhive.agentCpuQuota` /
+`agentMemoryMax` for one agent, persisted to
+`meta/resource-limits.json` (see
+[`persistence.md`](../persistence.md)). Values are systemd's
+`CPUQuota=` / `MemoryMax=` syntax: a percentage (`400%` = four full
+cores) for CPU; a size (`8G`), a percentage of physical RAM, or
+`infinity` for memory. Both are validated before they're persisted —
+they go into a systemd drop-in verbatim, and a typo there makes the
+unit fail to start.
+
+**Declarative, not incremental**: each invocation replaces the agent's
+whole entry. `set-limits sock --memory-max 8G` leaves `sock` with *only*
+a memory override, reverting any previously-set CPU quota to the hive
+default. To avoid a forgotten flag silently wiping an override, a bare
+`set-limits <name>` with no flags is rejected — clearing requires the
+explicit `--reset`.
+
+The command rewrites the container's drop-in and reloads systemd, so
+new containers and restarts pick the values up immediately.
+
 ## Choom
 
 Drop into an interactive Claude session inside an agent container.