subagents extension on the generic host surfaces

The rock now owns all subagent policy on top of libpanto-lua's generic APIs:
children are ordinary panto.agent instances over rock-constructed stores,
started with agent:run_async and awaited by arming uv.new_poll on each job's
wake_fd from the tool handler's coroutine.

subagents/jobs.lua carries the session policy the host used to own: the
concurrency gate (4 running, FIFO queue, cancel-while-queued never starts),
the await contract (results in input order; "first" returns settled plus
remaining by identity), and settle-time shaping. subagents/spawn.lua seeds
new children (primary system context, child role, profile body with manifest
metadata), resolves model/reasoning through panto.ext.resolve_model, filters
subagents.* out of the inherited tool set via agent:set_tools, and reads
resume defaults back from stored message metadata. One-shot structured
workers are a null_store agent with a declaration-only output tool,
tool_choice forced, dispatch_tools=false. subagents/progress.lua renders
per-tool-entry cards through the component handle's invalidate seam;
turn_interrupt cancels live children, turn_end closes them.

Spec suite rewritten against fakes of the new surfaces (98 cases), including
gate/queue/cancel bounds, resume-default extraction, one-shot capture via
unresolved tool calls, tool filtering, and manifest seeding.

1 files changed, 88 insertions, 0 deletions

diff --git a/spec/test_frontmatter.lua b/spec/test_frontmatter.lua
new file mode 100644
index 0000000..3f0c4c5
--- /dev/null
+++ b/spec/test_frontmatter.lua
@@ -0,0 +1,88 @@
+-- subagents/frontmatter.lua: splitting a profile into YAML header and body.
+--
+-- The body is the part a broken header must never cost the user, so every
+-- degraded case is checked for "body preserved verbatim" as well as for the
+-- warning. Cases that actually parse YAML need lyaml and skip without it.
+
+local frontmatter = require("subagents.frontmatter")
+
+local function lyaml_or_skip()
+    return pcall(require, "lyaml")
+end
+
+return {
+    { "fenced header parses and keeps the body verbatim", function()
+        if not lyaml_or_skip() then
+            return "skip", "lyaml is not installed"
+        end
+        local body = "You are a reviewer.\n\n  indented line  \n"
+        local data, parsed_body, warning = frontmatter.parse(
+            "---\nname: reviewer\ndescription: Reviews changes\nmodel: anthropic:sonnet\n---\n" .. body)
+        assert(warning == nil, "unexpected warning: " .. tostring(warning))
+        assert(type(data) == "table", "expected a mapping")
+        assert(data.name == "reviewer", tostring(data.name))
+        assert(data.description == "Reviews changes")
+        assert(data.model == "anthropic:sonnet", tostring(data.model))
+        assert(parsed_body == body, string.format("body was rewritten: %q", parsed_body))
+    end },
+
+    { "CRLF fences are tolerated", function()
+        if not lyaml_or_skip() then
+            return "skip", "lyaml is not installed"
+        end
+        local data, body, warning = frontmatter.parse("---\r\nname: crlf\r\n---\r\nbody\r\n")
+        assert(warning == nil, tostring(warning))
+        assert(type(data) == "table" and data.name == "crlf", "header did not parse")
+        assert(body == "body\r\n", string.format("%q", body))
+    end },
+
+    { "no fence means the whole file is the body", function()
+        local text = "You are a reviewer.\n\n---\n\nNot a header.\n"
+        local data, body, warning = frontmatter.parse(text)
+        assert(data == nil, "expected no metadata")
+        assert(body == text, "body was rewritten")
+        assert(warning == nil, tostring(warning))
+    end },
+
+    { "an unterminated fence is treated as prose", function()
+        local text = "---\nname: never closed\n\nstill prose\n"
+        local data, body, warning = frontmatter.parse(text)
+        assert(data == nil, "expected no metadata")
+        assert(body == text, "body was rewritten")
+        assert(warning == nil, "a lone rule is not an error")
+    end },
+
+    { "an empty fenced block is an empty mapping", function()
+        local data, body, warning = frontmatter.parse("---\n---\nbody\n")
+        assert(type(data) == "table" and next(data) == nil, "expected an empty mapping")
+        assert(body == "body\n", string.format("%q", body))
+        assert(warning == nil, tostring(warning))
+    end },
+
+    { "broken YAML warns and keeps the body", function()
+        if not lyaml_or_skip() then
+            return "skip", "lyaml is not installed"
+        end
+        local data, body, warning = frontmatter.parse("---\na: [unclosed\n---\nbody\n")
+        assert(data == nil, "a broken header must not produce metadata")
+        assert(body == "body\n", string.format("%q", body))
+        assert(type(warning) == "string" and warning:find("did not parse", 1, true),
+            "expected a parse warning, got " .. tostring(warning))
+    end },
+
+    { "a non-mapping document warns and keeps the body", function()
+        if not lyaml_or_skip() then
+            return "skip", "lyaml is not installed"
+        end
+        local data, body, warning = frontmatter.parse("---\njust a string\n---\nbody\n")
+        assert(data == nil, "a scalar header must not produce metadata")
+        assert(body == "body\n", string.format("%q", body))
+        assert(type(warning) == "string" and warning:find("not a mapping", 1, true),
+            "expected a mapping warning, got " .. tostring(warning))
+    end },
+
+    { "empty input is empty output", function()
+        local data, body, warning = frontmatter.parse("")
+        assert(data == nil and body == "" and warning == nil)
+    end },
+}