feat(bild): adaptive terminal output with width detection

- Add Omni/Log/Terminal module to detect terminal capabilities -
Implement 3 output modes: RichMultiLine (≥80 cols), SingleLine
(40-79),
  SimpleFallback (<40 or dumb terminals)
- Terminal width auto-detection via System.Console.ANSI.getTerminalSize
- Text truncation with ellipsis to prevent line wrapping - Manual
override via BILD_OUTPUT_MODE env var (simple|single|rich|auto)

Fixes UI corruption on small terminals (mobile SSH, narrow windows).
Wide terminals keep existing multi-line behavior but with truncation.

Design doc: _/llm/CONCURRENT_LOG_DESIGN.md

1 files changed, 78 insertions, 0 deletions

diff --git a/Omni/Log/Terminal.hs b/Omni/Log/Terminal.hs
new file mode 100644
index 0000000..1230eb3
--- /dev/null
+++ b/Omni/Log/Terminal.hs
@@ -0,0 +1,78 @@
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+
+-- | Terminal detection and output mode selection
+module Omni.Log.Terminal
+  ( TerminalInfo (..),
+    OutputMode (..),
+    detectTerminal,
+    truncateToWidth,
+  )
+where
+
+import Alpha
+import qualified Data.Text as Text
+import qualified System.Console.ANSI as ANSI
+import qualified System.Environment as Env
+
+data OutputMode
+  = RichMultiLine -- Wide terminals (≥80 cols)
+  | SingleLine -- Narrow terminals (40-79 cols)
+  | SimpleFallback -- Very narrow (<40) or dumb terminals
+  deriving (Eq, Show)
+
+data TerminalInfo = TerminalInfo
+  { tiWidth :: Int,
+    tiHeight :: Int,
+    tiMode :: OutputMode,
+    tiSupportsANSI :: Bool
+  }
+  deriving (Eq, Show)
+
+detectTerminal :: IO TerminalInfo
+detectTerminal = do
+  term <- Env.lookupEnv "TERM"
+  area <- Env.lookupEnv "AREA"
+  modeOverride <- Env.lookupEnv "BILD_OUTPUT_MODE"
+
+  -- Check if we support ANSI
+  let supportsANSI = case (term, area) of
+        (Just "dumb", _) -> False
+        (_, Just "Live") -> False -- production logs
+        (Nothing, _) -> False
+        _ -> True
+
+  -- Get terminal size
+  mSize <- ANSI.getTerminalSize
+  let (width, height) = case mSize of
+        Just (h, w) -> (w, h)
+        Nothing -> (80, 24) -- sensible default
+
+  -- Determine mode
+  let autoMode
+        | not supportsANSI = SimpleFallback
+        | width < 40 = SimpleFallback
+        | width < 80 = SingleLine
+        | otherwise = RichMultiLine
+
+  -- Allow manual override
+  let mode = case modeOverride of
+        Just "simple" -> SimpleFallback
+        Just "single" -> SingleLine
+        Just "rich" -> RichMultiLine
+        _ -> autoMode
+
+  pure
+    TerminalInfo
+      { tiWidth = width,
+        tiHeight = height,
+        tiMode = mode,
+        tiSupportsANSI = supportsANSI
+      }
+
+-- | Truncate text to fit width with ellipsis
+truncateToWidth :: Int -> Text -> Text
+truncateToWidth maxWidth text
+  | Text.length text <= maxWidth = text
+  | maxWidth <= 3 = Text.take maxWidth text
+  | otherwise = Text.take (maxWidth - 3) text <> "..."