Make web document navigation survive live-updating pages

Recreated-node caret recovery, tolerant caret validation, per-root retained document trees and cursors across tab switches, document warm-up, coalesced structural moves, and hung-provider fast-fail with an 'Application is not responding' announcement.

internal/review/document_requests.go

@@ -23,12 +23,23 @@ import (
 	"time"
 )
 
+// WarmDocument captures and syncs the currently focused document in the
+// background so the first navigation key does not pay for a cold capture.
+// Best-effort: a full queue or a focus outside web content is ignored by
+// the worker, and no result is delivered.
+func (worker *Worker) WarmDocument() {
+	select {
+	case worker.requests <- request{documentEpoch: worker.documentEpoch.Load(), documentLoadEpoch: worker.documentLoadEpoch.Load(), warmDocument: true, queuedAt: time.Now()}:
+	default:
+	}
+}
+
 func (worker *Worker) MoveDocumentCaret(command DocumentCaretCommand) error {
 	if !command.valid() {
 		return ErrInvalidDirection
 	}
 	select {
-	case worker.requests <- request{documentEpoch: worker.documentEpoch.Load(), caretCommand: command, queuedAt: time.Now()}:
+	case worker.requests <- request{documentEpoch: worker.documentEpoch.Load(), documentLoadEpoch: worker.documentLoadEpoch.Load(), caretCommand: command, queuedAt: time.Now()}:
 		return nil
 	default:
 		return ErrRequestQueueFull
@@ -37,7 +48,7 @@ func (worker *Worker) MoveDocumentCaret(command DocumentCaretCommand) error {
 
 func (worker *Worker) ActivateDocumentCaret() error {
 	select {
-	case worker.requests <- request{documentEpoch: worker.documentEpoch.Load(), activate: true, queuedAt: time.Now()}:
+	case worker.requests <- request{documentEpoch: worker.documentEpoch.Load(), documentLoadEpoch: worker.documentLoadEpoch.Load(), activate: true, queuedAt: time.Now()}:
 		return nil
 	default:
 		return ErrRequestQueueFull
@@ -49,7 +60,7 @@ func (worker *Worker) ReadAll(ctx context.Context) error {
 		return errors.New("read all: nil context")
 	}
 	select {
-	case worker.requests <- request{documentEpoch: worker.documentEpoch.Load(), readAll: ctx, queuedAt: time.Now()}:
+	case worker.requests <- request{documentEpoch: worker.documentEpoch.Load(), documentLoadEpoch: worker.documentLoadEpoch.Load(), readAll: ctx, queuedAt: time.Now()}:
 		return nil
 	default:
 		return ErrRequestQueueFull
@@ -61,7 +72,7 @@ func (worker *Worker) JumpToDocumentFragment(fragment string) error {
 		return ErrInvalidDirection
 	}
 	select {
-	case worker.requests <- request{documentEpoch: worker.documentEpoch.Load(), fragment: fragment, queuedAt: time.Now()}:
+	case worker.requests <- request{documentEpoch: worker.documentEpoch.Load(), documentLoadEpoch: worker.documentLoadEpoch.Load(), fragment: fragment, queuedAt: time.Now()}:
 		return nil
 	default:
 		return ErrRequestQueueFull