Slate React shell buttons must be internal targets

Problem

Large-document shell buttons are app/internal controls. If their keydown events bubble into Editable as editor events, the kernel can classify shell activation as a native-owned editor command.

Symptoms

• A generated shell activation gauntlet failed with command cannot be native-owned.
• The hand-authored shell activation row still passed because it asserted the final selection, not the kernel transition.
• The failure appeared only after generated gauntlets started checking illegal transitions.

What Didn't Work

• Treating the hand-authored row as sufficient. It proved behavior, not ownership.
• Asserting DOM selection for shell activation. Shell activation is model-backed and intentionally does not rely on DOM focus selection.

Solution

Treat role-button and contenteditable=false descendants as internal targets in the editable input classifier.

Generated shell activation proofs should assert model selection through the Slate browser handle, not DOM selection.

Why This Works

Shell activation belongs to the shell control, not the editor native input path. Classifying shell controls as internal targets prevents Editable from recording a command while also marking the event as native-owned.

Prevention

• Generated gauntlets should check illegal kernel transitions, not just final model state.
• Shell-backed selection proofs should say whether they assert model selection or DOM selection.
• Any contenteditable=false interactive descendant should be reviewed as an internal target before adding editor-level key handling.

Related Issues

• Slate browser selectionchange proof must separate traceability from programmatic import