feat(ava): subagent hardening with audit logging

Based on Anthropic's effective harnesses research.

New modules:
- Omni/Agent/AuditLog.hs: JSONL audit logging with SubagentId linking
- Omni/Agent/Tools/AvaLogs.hs: Tool for Ava to query her own logs
- Omni/Agent/Subagent/HARDENING.md: Design documentation

Key features:
- SubagentHandle with TVar status for async execution and polling
- spawnSubagentAsync, querySubagentStatus, waitSubagent, cancelSubagent
- User confirmation: spawn_subagent requires confirmed=true after approval
- Audit logs stored in $AVA_DATA_ROOT/logs/{ava,subagents}/
- CLI: ava logs [--last=N] [<subagent_id>]
- read_ava_logs tool for Ava self-diagnosis

Tasks: t-267, t-268, t-269, t-270, t-271

1 files changed, 109 insertions, 0 deletions

diff --git a/Omni/Agent/Tools/AvaLogs.hs b/Omni/Agent/Tools/AvaLogs.hs
new file mode 100644
index 0000000..582b3a6
--- /dev/null
+++ b/Omni/Agent/Tools/AvaLogs.hs
@@ -0,0 +1,109 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+
+-- | Tool for Ava to read her own audit logs and subagent traces.
+--
+-- Enables self-diagnosis: "Let me check my logs for that subagent run..."
+--
+-- : out omni-agent-tools-avalogs
+-- : dep aeson
+-- : dep time
+module Omni.Agent.Tools.AvaLogs
+  ( readAvaLogsTool,
+    main,
+  )
+where
+
+import Alpha
+import Data.Aeson ((.=))
+import qualified Data.Aeson as Aeson
+import qualified Data.Aeson.Key as Key
+import qualified Data.Aeson.KeyMap as KeyMap
+import qualified Data.Text as Text
+import qualified Data.Time as Time
+import qualified Omni.Agent.AuditLog as AuditLog
+import qualified Omni.Agent.Engine as Engine
+
+main :: IO ()
+main = putText "Omni.Agent.Tools.AvaLogs - no standalone execution"
+
+readAvaLogsTool :: Engine.Tool
+readAvaLogsTool =
+  Engine.Tool
+    { Engine.toolName = "read_ava_logs",
+      Engine.toolDescription =
+        "Read Ava's audit logs or subagent traces for self-diagnosis. "
+          <> "Use to review past conversations, inspect subagent runs, or debug issues. "
+          <> "Pass subagent_id to view a specific subagent's trace, or last_n for recent Ava logs.",
+      Engine.toolJsonSchema =
+        Aeson.object
+          [ "type" .= ("object" :: Text),
+            "properties"
+              .= Aeson.object
+                [ "subagent_id"
+                    .= Aeson.object
+                      [ "type" .= ("string" :: Text),
+                        "description" .= ("Subagent ID to view (e.g. 'abc123')" :: Text)
+                      ],
+                  "last_n"
+                    .= Aeson.object
+                      [ "type" .= ("integer" :: Text),
+                        "description" .= ("Number of recent log entries to return (default: 20)" :: Text)
+                      ]
+                ]
+          ],
+      Engine.toolExecute = executeReadLogs
+    }
+
+executeReadLogs :: Aeson.Value -> IO Aeson.Value
+executeReadLogs v = do
+  let maybeSubagentId = case v of
+        Aeson.Object obj -> case KeyMap.lookup "subagent_id" obj of
+          Just (Aeson.String sid) -> Just sid
+          _ -> Nothing
+        _ -> Nothing
+
+  let lastN = case v of
+        Aeson.Object obj -> case KeyMap.lookup "last_n" obj of
+          Just (Aeson.Number n) -> round n
+          _ -> 20
+        _ -> 20
+
+  case maybeSubagentId of
+    Just sid -> do
+      let subagentId = AuditLog.SubagentId sid
+      entries <- AuditLog.readSubagentLogs subagentId
+      pure
+        <| Aeson.object
+          [ "subagent_id" .= sid,
+            "entry_count" .= length entries,
+            "entries" .= map formatEntry entries
+          ]
+    Nothing -> do
+      entries <- AuditLog.getRecentAvaLogs lastN
+      today <- Time.utctDay </ Time.getCurrentTime
+      pure
+        <| Aeson.object
+          [ "date" .= Time.formatTime Time.defaultTimeLocale "%Y-%m-%d" today,
+            "entry_count" .= length entries,
+            "entries" .= map formatEntry entries
+          ]
+
+formatEntry :: AuditLog.AuditLogEntry -> Aeson.Value
+formatEntry entry =
+  Aeson.object
+    [ "timestamp" .= Time.formatTime Time.defaultTimeLocale "%H:%M:%S" (AuditLog.logTimestamp entry),
+      "event_type" .= tshow (AuditLog.logEventType entry),
+      "agent_id" .= AuditLog.unAgentId (AuditLog.logAgentId entry),
+      "content" .= summarizeContent (AuditLog.logContent entry)
+    ]
+
+summarizeContent :: Aeson.Value -> Text
+summarizeContent (Aeson.String t) = Text.take 200 t
+summarizeContent (Aeson.Object obj) =
+  let keys = KeyMap.keys obj
+   in "object with keys: " <> Text.intercalate ", " (map Key.toText keys)
+summarizeContent (Aeson.Array arr) = "array with " <> tshow (length arr) <> " items"
+summarizeContent Aeson.Null = "null"
+summarizeContent (Aeson.Bool b) = if b then "true" else "false"
+summarizeContent (Aeson.Number n) = tshow n