fix(tui): move Sigwinch behind unix build constraints — unbreaks windows CI (release gate)

internal/tui/loopimpl.go

@@ -1085,14 +1085,6 @@ func (e *TermEnv) Sigint() <-chan os.Signal {
 	return sig
 }
 
-// Sigwinch subscribes to terminal resizes (FR-TUI-P-04) so the loop can
-// re-probe the geometry and repaint promptly instead of at the next poll.
-func (e *TermEnv) Sigwinch() <-chan os.Signal {
-	sig := make(chan os.Signal, 1)
-	signal.Notify(sig, syscall.SIGWINCH)
-	return sig
-}
-
 // SuspendAttach runs `herdr --session <s> agent attach <paneId>` with
 // inherited stdio, exactly what `devagent attach <task> --exec` does
 // (FR-VIS-02). The resolved pane id is recorded in the orchestration ledger

internal/tui/rawterm_other.go

@@ -2,7 +2,10 @@
 
 package tui
 
-import "errors"
+import (
+	"errors"
+	"os"
+)
 
 // rawTerm is a no-op stub on platforms without the POSIX termios interface:
 // the interactive loop refuses to start (the non-TTY one-shot path never
@@ -16,3 +19,10 @@ func (r *rawTerm) enterRaw() error { return errors.New("raw mode unsupported on
 func (r *rawTerm) restore() {}
 
 func termSize(fd int) (rows, cols int) { return DefaultRows, DefaultColumns }
+
+// Sigwinch is a stub on platforms without SIGWINCH (Windows). The TermEnv
+// contract (loop.go) allows a nil channel: Run's resize select simply never
+// fires and the poll path repaints instead.
+func (e *TermEnv) Sigwinch() <-chan os.Signal {
+	return nil
+}

internal/tui/rawterm_unix.go

@@ -9,6 +9,8 @@ package tui
 // syscall — the same IFMIN..IFLAG word layout IoctlGetTermios manages.
 
 import (
+	"os"
+	"os/signal"
 	"syscall"
 	"unsafe"
 )
@@ -78,3 +80,13 @@ func termSize(fd int) (rows, cols int) {
 	}
 	return int(ws.Row), int(ws.Col)
 }
+
+// Sigwinch subscribes to terminal resizes (FR-TUI-P-04) so the loop can
+// re-probe the geometry and repaint promptly instead of at the next poll.
+// Unix-only: syscall.SIGWINCH does not exist on Windows — the TermEnv
+// contract (loop.go: may return nil) covers the stub there.
+func (e *TermEnv) Sigwinch() <-chan os.Signal {
+	sig := make(chan os.Signal, 1)
+	signal.Notify(sig, syscall.SIGWINCH)
+	return sig
+}