doc: silence rustdoc intra-doc warnings (private-item links and palette/surface ambiguities)

`cargo doc --no-deps` was emitting eight warnings about intra-doc links resolving to private items or ambiguous fn/module names. None reflect a behaviour bug; they were just noise that cluttered the docs build output.
Five of the warnings came from doc comments that cross-referenced items not in the rendered public API. `widget::scroll::Scroll` (struct), `Scroll::horizontal`, `Scroll::both`, `event_loop::text_editing` (module) and `text_shaping` (module) are all `pub` in their own modules, but the `widget` and `event_loop` parents are private to the crate root, so rustdoc treats them as private when resolving links from items that ARE on the public surface (`ScrollAxis`, the `scroll` constructor, `font_bytes`, the `text_edit` module docs). The fix is to drop the link syntax for those references: keep the identifier in backticks (so it still renders as code) but remove the surrounding `[...]` so rustdoc doesn't try to resolve it. Where the cross-reference had no semantic load beyond "see this module", the prose is rephrased to name the module without trying to link to it (e.g. "the `event_loop::text_editing` private module", "see the `text_shaping` private module").
The remaining three warnings were `palette` / `surface` linking ambiguously between a module of that name and a function of the same name within `crate::theme`. Adding `()` after the identifier inside the brackets (`palette` → `palette()`, `surface` → `surface()`) disambiguates to the function, which is the intent in all three sites — the surrounding text talks about "per-slot shorthand accessors", which is what the functions are.
After this `cargo doc --no-deps` runs clean with no warnings.

src/widget/scroll/mod.rs

@@ -8,7 +8,7 @@ use crate::widget::Element;
 #[cfg(test)]
 mod tests;
 
-/// Which axes a [`Scroll`] viewport allows to move along. Determines
+/// Which axes a `Scroll` viewport allows to move along. Determines
 /// whether the layout grows the child past the viewport width, the
 /// viewport height, or both, and which axis gesture / wheel deltas
 /// route to.
@@ -139,7 +139,7 @@ pub(crate) fn clamp_offset( offset: f32, content_h: f32, viewport_h: f32 ) -> f3
 }
 
 /// Create a scrollable viewport wrapping `child`. Defaults to vertical
-/// scrolling; chain [`Scroll::horizontal`] or [`Scroll::both`] to
+/// scrolling; chain `Scroll::horizontal` or `Scroll::both` to
 /// switch axes.
 ///
 /// The parent layout controls the viewport size by assigning a rect to

src/widget/text_edit/mod.rs

@@ -4,7 +4,7 @@
 //! Text input field — single-line or multiline. The widget itself
 //! owns layout / draw; the runtime side of text editing
 //! (insert, delete, cursor movement, selection, clipboard)
-//! lives in [`crate::event_loop::text_editing`].
+//! lives in the `event_loop::text_editing` private module.
 
 use std::sync::Arc;