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/theme/palette.rs

@@ -51,7 +51,7 @@ impl Palette
 	/// (`bg-page`, `surface`, `surface-alt`, `text-primary`,
 	/// `text-secondary`, `accent`, `divider`, `icon`). Missing slots
 	/// fall back to a documented sensible default so downstream widgets
-	/// never see uninitialised colours. Used by [`crate::theme::palette`] and
+	/// never see uninitialised colours. Used by [`crate::theme::palette()`] and
 	/// [`crate::theme::window_controls`].
 	pub fn from_slots( slots: &SlotStore ) -> Self
 	{