swarm: per-agent inference settings (model, effort, subagent_models) in KV

swarm-controller keeps each agent's inference settings in a new
`agent-inference` KV bucket, one key per agent, and is its only writer
(`GET`/`PUT`/`DELETE /api/agents/{name}/inference`; `swarmctl agent
inference get|set|clear`). Every field is optional. Each agent reads its
own key every 10 s through a direct-get grant on that key alone, and a
set `model` or `effort` replaces the Bus value, so the next turn runs on
it and the badge follows.

The swarm value is applied without persisting it: `Bus::set_model` and
`set_effort` are split into a persisting setter and a non-persisting
`apply_*`, and the poller uses the latter. Otherwise the swarm value
would overwrite `hyperhive-model`/`hyperhive-effort`, and clearing it, or
a restart, would no longer find the agent's own value. An unset field
changes nothing; a field cleared after being applied goes back to the
local value (`harness_state::local_model`/`local_effort`, the same
resolution `Bus::new` uses), read again at the clear.

`subagent_models` is validated, stored and shown by `get`; no agent
applies it yet.

Refs #5034

docs/tools/swarmctl-cli.md

@@ -9,6 +9,10 @@ This document contains the help content for the `swarmctl` command-line program.
 * [`swarmctl agent create`↴](#swarmctl-agent-create)
 * [`swarmctl agent mint-identity`↴](#swarmctl-agent-mint-identity)
 * [`swarmctl agent mint-forge-token`↴](#swarmctl-agent-mint-forge-token)
+* [`swarmctl agent inference`↴](#swarmctl-agent-inference)
+* [`swarmctl agent inference get`↴](#swarmctl-agent-inference-get)
+* [`swarmctl agent inference set`↴](#swarmctl-agent-inference-set)
+* [`swarmctl agent inference clear`↴](#swarmctl-agent-inference-clear)
 * [`swarmctl schedule`↴](#swarmctl-schedule)
 * [`swarmctl schedule add`↴](#swarmctl-schedule-add)
 * [`swarmctl schedule list`↴](#swarmctl-schedule-list)
@@ -59,6 +63,7 @@ Manage agents across the swarm
 * `create` — Queue creation of a new agent on a hive in this swarm
 * `mint-identity` — Queue a re-mint of an existing agent's identity at the swarm's secret store
 * `mint-forge-token` — Check one agent's forge token, and mint it if it's missing or stale
+* `inference` — Show or change the model, effort and subagent models the swarm sets for an agent
 
 
 
@@ -137,6 +142,82 @@ Queues and returns, the same way `agent create` does — watch the swarm UI's jo
 
 
 
+## `swarmctl agent inference`
+
+Show or change the model, effort and subagent models the swarm sets for an agent.
+
+A field the swarm sets wins over the agent's own value (from its `/model` or `/effort` pick or its agent.nix) from its next turn on; the agent reads its settings every ten seconds. A field the swarm doesn't set, or clears, leaves the agent on its own value.
+
+**Usage:** `swarmctl agent inference <COMMAND>`
+
+###### **Subcommands:**
+
+* `get` — Show what the swarm sets for an agent, naming the fields it doesn't set
+* `set` — Set fields for an agent. Only the flags given change; the others keep what's stored
+* `clear` — Clear every field for an agent, so it goes back to its own values
+
+
+
+## `swarmctl agent inference get`
+
+Show what the swarm sets for an agent, naming the fields it doesn't set
+
+**Usage:** `swarmctl agent inference get [OPTIONS] <AGENT>`
+
+###### **Arguments:**
+
+* `<AGENT>` — Agent name
+
+###### **Options:**
+
+* `--controller-socket <PATH>` — swarm-controller's unix socket.
+
+   Supplied by the nix module that installs this binary, from the same `socketPath` option the daemon binds; falls back to `SWARM_CONTROLLER_SOCKET`.
+
+
+
+## `swarmctl agent inference set`
+
+Set fields for an agent. Only the flags given change; the others keep what's stored
+
+**Usage:** `swarmctl agent inference set [OPTIONS] <AGENT>`
+
+###### **Arguments:**
+
+* `<AGENT>` — Agent name. A hive must declare it
+
+###### **Options:**
+
+* `--model <MODEL>` — The model its turns run on, as claude's `--model` takes it
+* `--effort <LEVEL>` — The reasoning effort its turns run at
+
+  Possible values: `low`, `medium`, `high`, `xhigh`, `max`
+
+* `--subagent-models <MODELS>` — The models it may start subagents on, comma-separated. Stored and shown; the agent doesn't apply it yet
+* `--controller-socket <PATH>` — swarm-controller's unix socket.
+
+   Supplied by the nix module that installs this binary, from the same `socketPath` option the daemon binds; falls back to `SWARM_CONTROLLER_SOCKET`.
+
+
+
+## `swarmctl agent inference clear`
+
+Clear every field for an agent, so it goes back to its own values
+
+**Usage:** `swarmctl agent inference clear [OPTIONS] <AGENT>`
+
+###### **Arguments:**
+
+* `<AGENT>` — Agent name
+
+###### **Options:**
+
+* `--controller-socket <PATH>` — swarm-controller's unix socket.
+
+   Supplied by the nix module that installs this binary, from the same `socketPath` option the daemon binds; falls back to `SWARM_CONTROLLER_SOCKET`.
+
+
+
 ## `swarmctl schedule`
 
 Manage scheduled prompts.