Root cause: normalize-box and slot :initforms used quoted literal
lists ('(...)) that were destructively modified by (setf (getf ...)).
Each call to normalize-box with a non-nil spec corrupted the shared
default list, causing all subsequent nodes with no explicit padding
to inherit the previous node's padding values.
Fix: replace all '(...) quoted literals with (list ...) constructor
calls — in normalize-box (3 paths) and in slot initforms for both
padding and margin.
All 11 test suites now pass: 358/358 checks, 0 failures.
- defslot: register render functions into named slots with ordering
- slot-render: call all registered render-fns for a slot
- Slot modes designed (stack/replace/single-winner) but mode dispatch
is implicit via the registration API
- slot-p, clear-slot, list-slots for lifecycle management
- Slots stored in a hash table keyed by string (equal test)
- 4 tests, 100% passing
- mouse-mixin class with on-mouse-down/up/move/scroll handler slots
- handle-mouse-event dispatches to the right handler by event type
- hit-test finds deepest component at (x,y) coordinates
- selection struct + get-selection + copy-to-clipboard
- SGR mouse parsing already existed in input system (mouse-event struct,
parse-sgr-mouse function, CSI dispatch in %read-escape-sequence)
- 3 tests, 100% passing
