Add background Lua workflows, inline child prompts, and layered config

subagents.lua now starts a workflow on its own coroutine and returns a
session-scoped id immediately, so fan-out continues while the primary keeps
working; completion wakes the primary, and later calls read immutable records
from subagents.workflows. Every ctx:agent takes a workflow-unique name so those
records are addressable. A session_start guidance message tells the primary when
to reach for run vs lua.

Children no longer inherit the primary's system context: a child starts from the
fixed child-role instruction plus its profile, and subagents.run/ctx:agent
accept an inline system_prompt instead of a profile. The now-redundant `agent`
form of subagents.models is gone.

Concurrency defaults to five and is configurable through [subagents]
max_concurrent in any layered config.toml; turn boundaries reap only settled
jobs so background workflows survive, while interrupt and session end cancel.

Config roots come from panto.ext.dirs.layers rather than a hand-rolled XDG
lookup, which picks up the base and git-ignored local layers for both agents/
and workflows/.

TOML workflows tighten up: the subagents.workflow tool takes a discovered name
only (inline `steps` duplicated subagents.lua at less power), an optional
top-level `output` array chooses the reported steps and their order instead of
the terminal set, a step with no workflow input gets no empty input heading, and
a workflow naming an undiscovered agent is rejected at discovery rather than
part-way through a run.

1 files changed, 33 insertions, 0 deletions

diff --git a/spec/fake_ext.lua b/spec/fake_ext.lua
index 5207e03..88c4b56 100644
--- a/spec/fake_ext.lua
+++ b/spec/fake_ext.lua
@@ -334,6 +334,7 @@ local function new_job(cfg)
         _events = cfg.events or {},
         _finish = cfg.finish,
         _harness = cfg.harness,
+        _wake_fd = cfg.wake_fd,
         _polls = 0,
         _settled = false,
         _result = nil,
@@ -372,6 +373,7 @@ function job_mt:result()
     elseif self._polls >= self._settle_after then
         self._result = self._finish(self)
     else
+        if self._wake_fd then pcall(require("luv").fs_write, self._wake_fd, "x", -1) end
         return nil
     end
     self._settled = true
@@ -488,6 +490,17 @@ function agent_mt:conversation()
     return self._conv
 end
 
+function agent_mt:add_system_message(text)
+    return self._conv:add_system_message(text)
+end
+
+function agent_mt:submit(value)
+    if not self._borrowed then
+        error("panto: submit is only available on the host session agent", 2)
+    end
+    self._harness.submissions[#self._harness.submissions + 1] = value
+end
+
 function agent_mt:set_message_metadata(index, metadata)
     self._record.final_metadata = metadata
     return true
@@ -552,6 +565,7 @@ function agent_mt:run_async(options)
         settle = outcome_for(h, record).settle,
         events = outcome_for(h, record).events,
         harness = h,
+        wake_fd = options.wake_fd,
         finish = function()
             return settled_result(h, record)
         end,
@@ -559,6 +573,7 @@ function agent_mt:run_async(options)
     h.jobs[#h.jobs + 1] = job
     record.job = job
     h.live = h.live + 1
+    if options.wake_fd then pcall(require("luv").fs_write, options.wake_fd, "x", -1) end
     if h.live > h.max_live then
         h.max_live = h.live
     end
@@ -609,6 +624,8 @@ function M.install(opts)
         commands_by_name = {},
         models_queries = {},
         subscriptions = {},
+        submissions = {},
+        emitted = {},
         on_by_name = {},
         mkdirs = made_dirs,
         queued = {},
@@ -653,6 +670,18 @@ function M.install(opts)
 
     local ext = {}
 
+    -- The host's layer list, in the same shape and order panto installs it.
+    ext.dirs = opts.dirs or {
+        home = "/home/u",
+        project_root = "/proj",
+        layers = {
+            { name = "base", dir = "/data/panto/agent" },
+            { name = "user", dir = "/home/u/.config/panto" },
+            { name = "project", dir = "/proj/.panto" },
+            { name = "local", dir = "/proj/.panto/local" },
+        },
+    }
+
     function ext.session_info()
         return copy(handle.session)
     end
@@ -697,6 +726,10 @@ function M.install(opts)
         handle.on_by_name[name] = fn
     end
 
+    function ext.emit(name)
+        handle.emitted[#handle.emitted + 1] = name
+    end
+
     -- Fire a subscribed lifecycle handler, the way the host would.
     function handle.emit(name, event)
         for _, subscription in ipairs(handle.subscriptions) do