fix(studio): flip per-slot binding presentation on bindings[…] edit acks

[Yona-Appletree]

Summary

• After authoring a binding via the slot detail popover, the per-slot binding presentation (authored vs default origin, Unbind affordance) lagged the passive project-read cadence — up to tens of seconds stale, worst when binding a slot to the same channel as its declared default (graph unchanged, only the origin flips). The engine/doc were correct immediately; only the Studio presentation lagged.
• Root cause: binding facts were derived from the synced slot tree only (during apply_tree_entry), while acked bindings[…] edits live in the overlay mirror until the next passive read.
• Fix: fact derivation now reads through the pending-edit mirror. A new BindingFactOverrides (in slot_binding_fact.rs) folds the overlay mirror's bindings[…] entries — shadowed by the local edit buffer, Failed entries skipped — into the synced authored facts. ProjectController::refresh_binding_presentation re-derives the whole tree's presentation (authored facts + graph-default overlay) after every applied project view and after every acked mutation that touched a bindings[…] path (or cleared the overlay/artifact wholesale, which can drop such entries). Unbind is symmetric: the acked entry removal drops the authored fact and the declared default refills immediately.
• Known residual (separate seam): rowless binding-derived rows (e.g. fixture.input, no backing slot row) build authored-vs-default from the binding-graph snapshot, which still refreshes passively.

Validation

• New controller test acked_bind_gesture_reads_authored_before_any_refresh: declared-default wiring on time, popover gesture to the same channel, scripted acks, no refresh → origin flips to authored, Unbind offered.
• New controller test acked_unbind_restores_default_presentation_before_any_refresh: one acked RemoveValue on the entry → default-origin presentation returns instantly.
• New end-to-end test bind_and_unbind_gestures_present_authored_state_from_acks_alone: drives the exact popover action sequence through the studio actor against the real in-process LpServer, asserting authored/unbound presentation from the acks alone (no RefreshProject in between).
• cargo test -p lpa-studio-core (455 passed), cargo test -p lpa-studio-web (117 passed), just check green.

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