windows-reactor dispatcher and internals review

[kennykerr]

Minor review and clean up of the dispatcher queue priority.

[Copilot]

Pull request overview

This PR refactors windows-reactor dispatcher priority handling to use WinUI’s DispatcherQueuePriority throughout, and updates contributor docs to better reflect current reactor internals and optimization ideas.

Changes:

• Replace the crate-local DispatchPriority with a re-export of DispatcherQueuePriority, updating dispatchers and tests accordingly.
• Simplify WinUI dispatcher enqueue logic to always use TryEnqueueWithPriority.
• Refresh docs/reactor-internals.md (codegen pipeline, threading/TLS inventory, and optimization notes).

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
docs/reactor-internals.md	Documentation cleanup + updated internals/optimization notes.
crates/tools/reactor/src/main.rs	Unify “write-if-changed” helpers and add optional rustfmt formatting toggle.
crates/libs/reactor/src/core/dispatcher.rs	Dispatcher API now takes DispatcherQueuePriority and updates internal test dispatchers.
crates/libs/reactor/src/core/render_host.rs	Update render scheduling to use DispatcherQueuePriority::{Normal,Low}.
crates/libs/reactor/src/winui/dispatcher.rs	Use TryEnqueueWithPriority for all priorities.
crates/tests/libs/reactor/tests/todo_smoke.rs	Update test dispatcher impl to new priority type.
crates/tests/libs/reactor/tests/render_stats.rs	Update test dispatcher impl to new priority type.
crates/tests/libs/reactor/tests/render_loop_coalesce.rs	Update priority-capturing dispatcher + assertions to new priority type.
crates/tests/libs/reactor/tests/host_effects.rs	Update queued job priority type to new priority type.
crates/tests/libs/reactor/tests/dispatcher.rs	Update RunOnDemandDispatcher tests to new priority type.