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, 3 insertions, 53 deletions

diff --git a/subagents/models.lua b/subagents/models.lua
index 511aa51..7272298 100644
--- a/subagents/models.lua
+++ b/subagents/models.lua
@@ -1,17 +1,12 @@
 -- The `subagents.models` tool: a bounded window onto the model catalog.
 --
 -- The catalog is far too large to inline into `subagents.run`'s description or
--- schema, so it is queried on demand instead. Four forms, chosen in this order:
+-- schema, so it is queried on demand instead. Three forms:
 --
---   { agent = "reviewer" }        what that profile will actually run on
 --   { model = "anthropic:sonnet"} exact lookup: wire name, reasoning levels
 --   { provider =, query =, limit=} bounded search
 --   { }                           inherited model/reasoning + provider counts
 --
--- The agent form is the join the primary actually wants before overriding a
--- profile: it reports the profile's own model, or says the profile inherits
--- the primary model and shows what that is.
---
 -- Results are short readable lines, not JSON. A truncated search says so
 -- explicitly so the primary refines the query instead of assuming it saw
 -- everything; `limit` is clamped to 1..50 (default 10) so no query can dump
@@ -22,8 +17,6 @@
 -- tool cannot confirm is still validated at spawn time — the catalog is
 -- advice, the runtime is authoritative.
 
-local spawn = require("subagents.spawn")
-
 local DEFAULT_LIMIT = 10
 local MAX_LIMIT = 50
 
@@ -143,52 +136,13 @@ local function clamp_limit(value)
     return limit
 end
 
--- The agent form: report the profile's effective model, or say it inherits.
-local function describe_agent(name, profiles)
-    profiles = spawn.profiles(profiles)
-    local profile = (profiles.by_name or {})[name]
-    if not profile then
-        return string.format("Error: unknown agent '%s'; known: %s", name, spawn.agent_names(profiles))
-    end
-
-    local out = { "agent: " .. profile.name }
-    if profile.description ~= "" then
-        out[#out + 1] = "description: " .. profile.description
-    end
-
-    if profile.model then
-        local result, err = ask({ model = profile.model })
-        if not result then
-            return "Error: " .. err
-        end
-        out[#out + 1] = format_exact(result, profile.model)
-    else
-        out[#out + 1] = "model: inherits the primary model"
-        local result, err = ask({})
-        if not result then
-            return "Error: " .. err
-        end
-        out[#out + 1] = format_overview(result)
-    end
-
-    if profile.reasoning then
-        out[#out + 1] = "profile reasoning: " .. profile.reasoning
-    end
-    return table.concat(out, "\n")
-end
-
-function M.handle(input, profiles)
+function M.handle(input)
     input = input or {}
     if type(input) ~= "table" then
         return "Error: expected a table of arguments."
     end
 
-    local agent, err = optional_string(input.agent, "agent")
-    if err then
-        return err
-    end
-    local model
-    model, err = optional_string(input.model, "model")
+    local model, err = optional_string(input.model, "model")
     if err then
         return err
     end
@@ -203,10 +157,6 @@ function M.handle(input, profiles)
         return err
     end
 
-    if agent then
-        return describe_agent(agent, profiles)
-    end
-
     if model then
         local result, ask_err = ask({ model = model })
         if not result then