Packages the proven editing-loop vertical slice as the API a GUI calls -- no UI,
no rendering backend of its own (it produces a RenderIR). EditorSession owns:
- selection state (Selection { source, layout_object }): click(point) selects the
topmost hit, select(id) restores a selection, selection()/clear_selection();
- render/hit-test query: render() and hit_test() for the GUI to draw and resolve
clicks/drags;
- operation minting -- the ergonomics gap the harness exposed, closed before UI
depends on it: the caller passes an OperationKind to apply() (or an intent like
transpose_selection(+1)) and the session assembles the OperationEnvelope (id,
author, stamp, causal context). A GUI never hand-rolls envelope bookkeeping;
- apply/re-render -- ATOMIC: a minted op the reducer rejects (e.g. a reserved
replica identity) returns Err(RejectedOperation), not a silent no-op, and a
diagnostic-only layout returns Err(NotRenderable); on any error nothing mutates,
operation counter included (the candidate id is committed only on success);
- selection preservation: the selection is re-resolved against the new layout,
kept when its layout object survives and cleared when it is gone.
The session is solver-agnostic (Box<dyn ConstraintSolver>), so a GUI plugs in the
Engraver, the stub, or any conformant solver. EditorError implements Display/Error.
epiphany-ops now re-exports AcceptOutcome (accept()'s return type, previously
unreachable) so a caller can inspect a rejection.
Also wires the edit-loop harness into the conformance suite as the [7c] UI-seam
gate: over both fixtures (ten_measure_single_staff and valid_score_rich) every seed
must drive a click->sharpen->re-render cycle whose selection survives the relayout
-- the contract a GUI's correctness rests on.
Full gate green: build, fmt, clippy, 606 tests, conformance scale 1 (incl. [7c]).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
