[tmm]

Description

The Rust conformance runner didn't replay property/sequences, the 81
random command sequences JS records on a rich-text editor with lists,
check lists, links, hashtags, code and history.

It does now. The suite builds the editor sequenceEditor builds, in the
extension builder's registration order: InitialStateExtension's first
update included, and no registerCodeIndentation, since only
CodeIndentExtension registers it.

Two Rust differences from JS showed up, and both are fixed:

• NormalizeInlineElementsExtension's registration (deleteEmptyInline,
  which RichTextExtension depends on) wasn't ported, so empty links and
  autolinks stayed. It is now register_normalize_inline_elements, behind
  the extension feature.
• In that editor, JS's getDOMSelection returns null, so
  $extendSelectionForDeletion and modify stop after their model step.
  Rust kept measuring and moved the selection into nearby text. A new
  SelectionMovement::has_dom_selection() (default true) lets an app say
  there is no DOM selection.

Test plan

Before

$ cargo run -q --release -p lexical-conformance | grep -E 'sequences|Total'
| `property/sequences` | – | – | – | – | – | not implemented |
| **Total** | 488 | 488 | 0 | 0 | 0 | |

After

$ cargo run -q --release -p lexical-conformance | grep -E 'sequences|Total'
| `property/sequences` | 81 | 81 | 0 | 0 | 0 | pass |
| **Total** | 569 | 569 | 0 | 0 | 0 | |
$ cargo test --workspace --all-features
38 passed, 0 failed

Mutations, each restored afterwards: delete_empty_inline removing
nothing fails 19 cases; the early return in
extend_selection_for_deletion disabled fails 6; FORMAT_TEXT_COMMAND
formatting nothing fails 15. doctored_sequences_fail checks that a
vector with one handled and one text changed fails exactly those
steps.

cargo fmt --check, clippy -D warnings, rustdoc -D warnings,
cargo +1.88 check, --no-default-features and Rune's clippy pass.

Stacked on #146.