the unplaceable word rides a typed error, not the message (V-634)

Recovering it by cutting on quotes in err.Error() meant the reply depended on
the wording of an error string. UnknownTargetError carries the word and
errors.Is still holds.

cmd/mavend/actions_act.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"errors"
 	"log"
-	"strings"
 
 	"github.com/kami/maven/internal/mcp"
 	"github.com/kami/maven/internal/phraser"
@@ -66,8 +65,12 @@ func (h *reactiveHandler) actionAct(ctx context.Context, dec router.Decision) st
 			// nothing ran. Saying which word she could not place is the whole
 			// answer: he either renames it or gives the row an alias that
 			// carries the target, and both are one turn away (V-634).
-			return phraser.A(phraser.ActUnknownTarget,
-				map[string]string{"name": unknownTargetOf(err, dec.Slots.Args)})
+			word := ""
+			var unknown *tool.UnknownTargetError
+			if errors.As(err, &unknown) {
+				word = unknown.Target
+			}
+			return phraser.A(phraser.ActUnknownTarget, map[string]string{"name": word})
 		case errors.Is(err, tool.ErrNeedsAuthedSurface):
 			// Irreversible (internal/tool/risk.go). A confirm turn would not
 			// help: everything that proposed this act — the STT, the router,
@@ -102,17 +105,3 @@ func (h *reactiveHandler) actionAct(ctx context.Context, dec router.Decision) st
 	return phraser.A(phraser.ActDone, nil)
 }
 
-// unknownTargetOf pulls the word the executor could not place out of its error,
-// falling back to the first arg. The word is what makes the reply usable, and a
-// reply naming no word would send him to the log.
-func unknownTargetOf(err error, args []string) string {
-	if _, rest, ok := strings.Cut(err.Error(), `"`); ok {
-		if word, _, ok := strings.Cut(rest, `"`); ok && word != "" {
-			return word
-		}
-	}
-	if len(args) > 0 {
-		return args[0]
-	}
-	return ""
-}