feat: term.update() folds CapabilityEvents into runtime capabilities - #133

Widen Update from { width, height } | CapabilityEvent to
{ width, height } | InputEvent. Events other than resize and capability
are no-op steps, so hosts can pass the full scan() events array without
filtering. Only ResizeEvent carries width/height, so the shapes stay
unambiguous. Matches the implementation in #133.

… them (renderer-spec §7.9)

Elements declare open(id, { pointerShape }). While
term.capabilities.pointerShape is true (raised by #132/#133 from the
probe's OSC 22 query reply), each render resolves the shape under the
pointer and appends `OSC 22 ; <shape> ST` to result.output when it
changes. The host keeps writing one buffer (cowboyd on #101). The
capability is the only gate; there is no createTerm option.

Everything lives in TypeScript; the wasm module and the packed encoding
are untouched, so there is no size or startup cost (#101 regressed
createTerm ~20% and grew the bundle 8.3 KB). Without the capability the
render path pays one boolean check and never reads pointerShape (a test
pins this with a counting getter). With it, the directive walk runs only
when the pointer is over something, and only a frame whose shape
changed copies output to append the sequence.

Resolution takes the last declaring id in Clay's pointer-over order:
pre-order within the topmost layer the pointer reaches, so the innermost
element wins and capture-mode floats hide what is beneath while
passthrough floats defer to it. snapshot() records its declared shapes
beside the packed bytes so pre-packed subtrees still participate.
Values outside the kitty/CSS vocabulary are ignored (and rejected by
validate()), so arbitrary strings never reach an OSC payload.

Restore (dreyfus92 on #101): set-only OSC 22 cannot pop, so the emitted
shape is the one piece of cross-frame state. It resets to "default"
when the pointer leaves or is omitted, and update() returns the reset
when the pointer-shape capability is withdrawn. Resize keeps it, since
the terminal's pointer did not change.

… them (renderer-spec §7.9)

Elements declare open(id, { pointerShape }). While
term.capabilities.pointerShape is true (raised by #132/#133 from the
probe's OSC 22 query reply), each render resolves the shape under the
pointer and appends `OSC 22 ; <shape> ST` to result.output when it
changes. The host keeps writing one buffer (cowboyd on #101). The
capability is the only gate; there is no createTerm option.

Everything lives in TypeScript; the wasm module and the packed encoding
are untouched, so there is no size or startup cost (#101 regressed
createTerm ~20% and grew the bundle 8.3 KB). Without the capability the
render path pays one boolean check and never reads pointerShape (a test
pins this with a counting getter). With it, the directive walk runs only
when the pointer is over something, and only a frame whose shape
changed copies output to append the sequence.

Resolution takes the last declaring id in Clay's pointer-over order:
pre-order within the topmost layer the pointer reaches, so the innermost
element wins and capture-mode floats hide what is beneath while
passthrough floats defer to it. snapshot() records its declared shapes
beside the packed bytes so pre-packed subtrees still participate.
Values outside the kitty/CSS vocabulary are ignored (and rejected by
validate()), so arbitrary strings never reach an OSC payload.

Restore (dreyfus92 on #101): set-only OSC 22 cannot pop, so the emitted
shape is the one piece of cross-frame state. It resets to "default"
when the pointer leaves or is omitted, and update() returns the reset
when the pointer-shape capability is withdrawn. Resize keeps it, since
the terminal's pointer did not change.