refactor(scenarios): add syntax highlighting and realistic Rust code (#118)

* refactor(scenarios): use realistic code content for basic/ and movement/ scenarios (WIP)

Updated scenarios to use multi-line Rust code instead of simple strings:
- basic/delete.toml, insert.toml, replace.toml
- movement/basic-movement.toml, word.toml, word-basics.toml
- movement/line.toml, line-navigation.toml

Work in progress - more files to update.

* feat(ui): add syntax highlighting and simplify scenarios

- Add syntect 5.3 for Rust syntax highlighting in editor view
- Create highlight.rs module with LazyLock for static initialization
- Use base16-eighties.dark theme for terminal display

Simplify scenarios to minimize text input (focus on commands):
- insert.toml: reduce typing to 0-2 characters per scenario
- repeat/basic-repeat.toml: simplify repeat_insert_001
- Fix cursor positions to match simulator behavior

All 141 scenarios pass execution tests.

* refactor(scenarios): update remaining scenarios with realistic Rust code

- Update clipboard/ scenarios (undo-redo, yank-paste)
- Update editing/ scenarios (delete-selection, indentation, join)
- Update movement/ scenarios (combined, document, find-till, goto-commands, match-brackets, precision)
- Update search/ scenarios (basic-search)
- Update selection/ scenarios (line-selection)
- Fix cursor rendering for end-of-line positions in highlight.rs

All 136 scenarios now use realistic Rust code snippets for proper
syntax highlighting.

* refactor(scenarios): complete realistic Rust code for remaining scenarios

- Update editing/advanced-editing.toml with Rust code
- Update editing/surround.toml with Rust code
- Update selection/advanced-selection.toml with Rust code
- Update repeat/basic-repeat.toml with Rust code
- Fix test expectations for repeat_insert_001 scenario

All 136 scenarios now use realistic Rust code snippets.

* fix(scenarios): update paragraph scenarios with realistic Rust code and selection

- Replace generic paragraph text with realistic Rust functions
- Add selection field to target state for ]p and [p commands
- These commands create a selection from original position to new position

This fixes the visual mismatch where target state didn't show the
selection that ]p/[p commands actually produce.

* release: prepare v0.5.3

- Bump version to 0.5.3
- Update README: 136 scenarios, Phase 2.2 status, remove Vim references
- Update CHANGELOG with v0.5.3 changes and fix version links
- Update HELIX_KEYBINDINGS.md: mark 90+ implemented commands

Author: bug-ops

CHANGELOG.md

@@ -7,6 +7,29 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.5.3] - 2026-01-09
+
+### Added
+
+- **Syntax highlighting for scenario code** — Rust code in scenarios now displays with full syntax highlighting using syntect
+- **Adaptive difficulty system** — Mini-game difficulty adjusts based on player performance metrics
+
+### Changed
+
+- **136 scenarios with realistic Rust code** — All scenarios updated from minimal synthetic text to real, idiomatic Rust code snippets
+- **Paragraph commands use Helix keybindings** — Changed from Vim-style `{`/`}` to Helix-style `[p`/`]p` paragraph navigation
+
+### Fixed
+
+- **Paragraph scenario selection visibility** — Target states now correctly show selection range for `]p`/`[p` commands
+- **Cursor rendering at end-of-line** — Cursor now displays correctly when positioned at the end of a line
+
+### Quality
+
+- **Tests**: 1239+ (up from 1116)
+- **Clippy**: Zero warnings
+- **Scenarios**: 136 total (realistic Rust code content)
+
 ## [0.5.2] - 2026-01-07
 
 ### Added
@@ -1037,7 +1060,10 @@ With this release, all Phase 1 components are fully implemented:
 
 ---
 
-[Unreleased]: https://github.com/bug-ops/helix-trainer/compare/v0.5.0...HEAD
+[Unreleased]: https://github.com/bug-ops/helix-trainer/compare/v0.5.3...HEAD
+[0.5.3]: https://github.com/bug-ops/helix-trainer/compare/v0.5.2...v0.5.3
+[0.5.2]: https://github.com/bug-ops/helix-trainer/compare/v0.5.1...v0.5.2
+[0.5.1]: https://github.com/bug-ops/helix-trainer/compare/v0.5.0...v0.5.1
 [0.5.0]: https://github.com/bug-ops/helix-trainer/compare/v0.4.8...v0.5.0
 [0.4.8]: https://github.com/bug-ops/helix-trainer/compare/v0.4.7...v0.4.8
 [0.4.7]: https://github.com/bug-ops/helix-trainer/compare/v0.4.6...v0.4.7