fix: multi-value backend-size, minibuffer border+width, pre-existing warnings

- backend-size: nested multiple-value-bind/values instead of or+mv-bind
  (or discards secondary values), remove stale env-var pre-check
- Minibuffer: full chat-w width (respects sidebar), horizontal rule
  border, clear filter prompt line to avoid text overlap
- Filter prompt: (or filter "") prevents "NIL" display
- Dirty-flag redraw: skip when dialog-stack is non-nil (minibuffer
  covers the area, prevents flicker)
- Remove 3 unused variables: FOCUS, SENSOR, C (pre-existing warnings)

org/channel-tui-main.org

@@ -209,7 +209,6 @@ Event handlers + daemon I/O + main loop.
                    ;; /context command — section breakdown with token estimates
                     ((string-equal text "/context")
                      (let* ((msg-count (length (st :messages)))
-                           (focus (or (st :foveal-id) "none"))
                             (id-tokens (min 200 (floor (+ 150 (length (or (st :focus-scope) ""))) 4)))
                            (tool-tokens (if (boundp 'passepartout::*cognitive-tool-registry*)
                                            (floor (* (hash-table-count passepartout::*cognitive-tool-registry*) 40) 4)
@@ -642,7 +641,6 @@ supplied (e.g. \"/\"), pre-fill the select filter with it."
          (msg-type (getf msg :type))
          (action (getf payload :action))
          (level (getf msg :level))
-         (sensor (getf payload :sensor))
          (gate-trace (getf msg :gate-trace))
          (rule-count (getf payload :rule-count))
          (foveal-id (getf payload :foveal-id)))
@@ -769,6 +767,7 @@ supplied (e.g. \"/\"), pre-fill the select filter with it."
                                  :name "tui-reader")
                   (return-from connect-daemon t))
              (usocket:connection-refused-error (c)
+                (declare (ignore c))
                 (when (= attempt 3)
                  (add-msg :system (format nil "* No daemon on port ~a after ~a attempts *"
                                          port attempt))))
@@ -994,7 +993,8 @@ supplied (e.g. \"/\"), pre-fill the select filter with it."
                ;; Guard w and h before render (resize or other code may have set them to nil)
                (setq w (or (and (numberp w) (> w 0) w) 80)
                      h (or (and (numberp h) (> h 0) h) 24))
-                              (when (or (first (st :dirty)) (second (st :dirty)) (third (st :dirty)))
+                               (when (and (or (first (st :dirty)) (second (st :dirty)) (third (st :dirty)))
+                                         (null (st :dialog-stack)))
                 (let* ((sidebar-w (if (and (st :sidebar-visible) (>= w 60))
                                        (or (st :sidebar-width) 30) 0))
                        (chat-w (- w sidebar-w)))
@@ -1013,21 +1013,26 @@ supplied (e.g. \"/\"), pre-fill the select filter with it."
                (let ((ds (st :dialog-stack)))
                   (when ds
                     (cl-tty.backend:begin-sync be)
-                   (let* ((dlg (car ds))
+                    (let* ((sidebar-w (if (and (st :sidebar-visible) (>= w 60))
+                                           (or (st :sidebar-width) 30) 0))
+                           (chat-w (- w sidebar-w))
+                           (dlg (car ds))
                            (sel (cl-tty.dialog:dialog-content dlg))
                            (filtered (cl-tty.select:select-filtered-options sel))
                            (sel-idx (cl-tty.select:select-selected-index sel))
                            (cnt (length filtered))
                            (filter (cl-tty.select:select-filter sel))
-                          ;; Bottom-anchored: filter at h-3, options above
                            (mh (min 15 (+ 1 cnt)))  ;; +1 for title
-                          (top (max 0 (- h 3 mh))))
-                     ;; Clear the full minibuffer area (top to h-2)
-                     (dotimes (r (min (- h 2 top) h))
-                       (cl-tty.backend:draw-rect be 0 (+ top r) w 1
+                           (top (max 0 (- h 4 mh))))
+                      ;; Clear the minibuffer area
+                      (dotimes (r (min (- h 3 top) h))
+                        (cl-tty.backend:draw-rect be 0 (+ top r) chat-w 1
                                                    :bg (theme-color :status-bg)))
-                     ;; Title line
+                      ;; Top border line with title
                       (cl-tty.backend:draw-text be 0 top
+                                                (make-string chat-w :initial-element #\─)
+                                                (theme-color :separator) nil)
+                      (cl-tty.backend:draw-text be 1 top
                                                 (cl-tty.dialog:dialog-title dlg)
                                                 (theme-color :accent) nil)
                       ;; Options
@@ -1049,8 +1054,10 @@ supplied (e.g. \"/\"), pre-fill the select filter with it."
                                                       nil :bold sel-p)
                             (incf y-off))))
                       ;; Filter prompt at h-3
+                      (cl-tty.backend:draw-rect be 0 (- h 3) chat-w 1
+                                                :bg (theme-color :status-bg))
                       (cl-tty.backend:draw-text be 0 (- h 3)
-                                               (format nil "> ~a" filter)
+                                                (format nil "> ~a" (or filter ""))
                                                 (theme-color :input-prompt) nil))
                     (cl-tty.backend:end-sync be))
                  (sleep 0.1))