hivectl: add hive-wide start/stop verbs

`hivectl stop` brings the whole hive down in one operator action — all
sub-agents plus the ci/forge/gateway/matrix infra containers — and
`hivectl start` brings it back up. Scope flags (--agents, --agent <name>,
--ci, --forge, --gateway, --matrix) narrow the set; a bare invocation
targets everything. hive-c0re never stops itself.

- hive-sh4re: HostRequest::{Stop,Start} + LifecycleScope wire type;
  priv_proto InfraAction + ControlInfraContainer + the
  CONTROLLABLE_INFRA_CONTAINERS allowlist (adds hive-matrix, excludes
  hive-c0re).
- hive-priv: control_infra_container handler (systemctl <verb>
  container@<name>, allowlist-validated root-side).
- hive-c0re: handle_stop / handle_start fan out agents via lifecycle and
  infra via hive-priv; per-target failures are aggregated. Infra
  systemctl routes through hive-priv (the privsep boundary).
- The --graceful flag is threaded through Stop now; the per-agent quiesce
  itself lands with the graceful-agent-stop work.

hive-c0re/src/bin/hivectl.rs

@@ -19,7 +19,7 @@ use std::os::unix::process::CommandExt as _;
 use std::path::{Path, PathBuf};
 
 use anyhow::{Context as _, Result, bail};
-use clap::{Parser, Subcommand};
+use clap::{Args, Parser, Subcommand};
 use hive_c0re::coordinator::Coordinator;
 
 #[derive(Parser)]
@@ -100,6 +100,36 @@ enum Cmd {
         #[arg(long)]
         fresh: bool,
     },
+    /// Stop containers hive-wide in one operator action. Bare `hivectl
+    /// stop` stops **everything** — all sub-agents plus the ci, forge,
+    /// gateway, and matrix infra containers. Narrow it with scope flags:
+    /// `--agents` (all sub-agents), `--ci` / `--forge` / `--gateway` /
+    /// `--matrix` (named infra), and `--agent <name>` (repeatable) for
+    /// specific sub-agents. Flags are additive (e.g. `--agents --matrix`).
+    /// Requires the hive-c0re daemon (connects to the host admin socket).
+    /// hive-c0re itself is never stopped — it services the request.
+    Stop {
+        #[command(flatten)]
+        scope: ScopeArgs,
+        /// Gracefully quiesce each agent (finish the current turn, drain
+        /// the inbox) before stopping, instead of a hard stop.
+        #[arg(long)]
+        graceful: bool,
+        /// Path to the hive-c0re host admin socket.
+        #[arg(long, default_value = DEFAULT_HOST_SOCKET)]
+        socket: PathBuf,
+    },
+    /// Start containers hive-wide — the inverse of `hivectl stop`. Bare
+    /// `hivectl start` starts everything back up; the same scope flags as
+    /// `stop` narrow it (`--agents`, `--ci`, `--forge`, `--gateway`,
+    /// `--matrix`, `--agent <name>`). Requires the hive-c0re daemon.
+    Start {
+        #[command(flatten)]
+        scope: ScopeArgs,
+        /// Path to the hive-c0re host admin socket.
+        #[arg(long, default_value = DEFAULT_HOST_SOCKET)]
+        socket: PathBuf,
+    },
     /// Emit the full CLI reference as `CommonMark` to stdout.
     ///
     /// Hidden tooling command (not part of day-to-day operator admin):
@@ -111,6 +141,49 @@ enum Cmd {
     MarkdownDocs,
 }
 
+/// Shared scope flags for `hivectl stop` / `hivectl start`. With no flag
+/// set the verb targets **everything** (all sub-agents + every controllable
+/// infra container). Setting any flag restricts to the selected classes,
+/// additively.
+// One bool per selectable container class, each mapping 1:1 to a clap flag;
+// orthogonal toggles, not a state machine — hence the bools allow (mirrors
+// `hive_sh4re::LifecycleScope`).
+#[allow(clippy::struct_excessive_bools)]
+#[derive(Args)]
+struct ScopeArgs {
+    /// All sub-agent containers.
+    #[arg(long)]
+    agents: bool,
+    /// A specific sub-agent by name. Repeatable: `--agent a --agent b`.
+    #[arg(long = "agent", value_name = "NAME")]
+    agent: Vec<String>,
+    /// The CI runner container (`hive-ci`).
+    #[arg(long)]
+    ci: bool,
+    /// The forge container (`hive-forge`).
+    #[arg(long)]
+    forge: bool,
+    /// The gateway container (`hive-gateway`).
+    #[arg(long)]
+    gateway: bool,
+    /// The matrix container (`hive-matrix`).
+    #[arg(long)]
+    matrix: bool,
+}
+
+impl ScopeArgs {
+    fn to_scope(&self) -> hive_sh4re::LifecycleScope {
+        hive_sh4re::LifecycleScope {
+            agents: self.agents,
+            agent_names: self.agent.clone(),
+            ci: self.ci,
+            forge: self.forge,
+            gateway: self.gateway,
+            matrix: self.matrix,
+        }
+    }
+}
+
 #[derive(Subcommand)]
 enum ForgeCmd {
     /// Create or refresh the Forgejo account + token for `<name>`.
@@ -348,6 +421,12 @@ async fn main() -> Result<()> {
             AgentsCmd::Restart { name, socket } => agents_restart(&socket, &name).await,
             AgentsCmd::RestartAll { socket } => agents_restart_all(&socket).await,
         },
+        Cmd::Stop {
+            scope,
+            graceful,
+            socket,
+        } => stop(&socket, scope.to_scope(), graceful).await,
+        Cmd::Start { scope, socket } => start(&socket, scope.to_scope()).await,
         Cmd::Choom { name, fresh } => choom(&name, fresh),
         Cmd::MarkdownDocs => {
             print!("{}", clap_markdown::help_markdown::<Cli>());
@@ -804,6 +883,43 @@ async fn agents_restart_all(socket: &Path) -> Result<()> {
     Ok(())
 }
 
+async fn stop(socket: &Path, scope: hive_sh4re::LifecycleScope, graceful: bool) -> Result<()> {
+    let resp =
+        hive_c0re::client::request(socket, hive_sh4re::HostRequest::Stop { scope, graceful })
+            .await
+            .with_context(|| format!("connect to daemon socket {}", socket.display()))?;
+    render_lifecycle(&resp, "stopped")
+}
+
+async fn start(socket: &Path, scope: hive_sh4re::LifecycleScope) -> Result<()> {
+    let resp = hive_c0re::client::request(socket, hive_sh4re::HostRequest::Start { scope })
+        .await
+        .with_context(|| format!("connect to daemon socket {}", socket.display()))?;
+    render_lifecycle(&resp, "started")
+}
+
+/// Render a hive-wide stop/start response: one `<verb>: <name>` line per
+/// touched container, then surface any aggregated per-target failure as a
+/// non-zero exit. `verb` is the past-tense word printed per item
+/// (`stopped` / `started`).
+fn render_lifecycle(resp: &hive_sh4re::HostResponse, verb: &str) -> Result<()> {
+    let items = resp.agents.as_deref().unwrap_or(&[]);
+    if items.is_empty() {
+        println!("{verb}: nothing matched the requested scope");
+    } else {
+        for item in items {
+            println!("{verb}: {item}");
+        }
+    }
+    if !resp.ok {
+        bail!(
+            "{verb}: {}",
+            resp.error.as_deref().unwrap_or("unknown error")
+        );
+    }
+    Ok(())
+}
+
 /// Reject usernames containing `:` (field separator) or control chars
 /// that would corrupt the htpasswd file format.
 fn validate_htpasswd_username(username: &str) -> Result<()> {