Expose a json codec to the subagents.lua sandbox

Model-authored workflow Lua could reach string, table, math, and utf8 but
had no way to parse an agent's report, so any fan-out over discovered work
had to invent an ad-hoc line format and hand-roll string.gmatch. Hand the
guest panto.ext.json instead. decode returns nil plus a message rather
than raising: the sandbox deliberately has no pcall, so a raising decoder
would let one malformed agent line kill an entire workflow.

Teach the pattern in the injected guidance too: deterministic Lua owns the
loops, counts, ordering, and gates, agents supply discovery and judgment,
and a worker that feeds Lua ends its report with one parseable line. The
existing static-graph example stays; a discover-then-fan-out example joins
it.

1 files changed, 1 insertions, 0 deletions

diff --git a/subagents/workflow.lua b/subagents/workflow.lua
index 3a59a8b..375285f 100644
--- a/subagents/workflow.lua
+++ b/subagents/workflow.lua
@@ -155,6 +155,7 @@ local function json_encode(value)
 end
 
 M.json_encode = json_encode
+M.json_decode = json_decode
 
 -- ---------------------------------------------------------------------------
 -- Schema validation