Add current-draft diagnostic underlines and passive hover

Preserve raw include diagnostic provenance and derive bands from the existing shaped editor. Retain deferred tooltip paragraphs through rendering. Include source, regression, failure and native-trial evidence; corrected native acceptance remains pending.

crates/vendor/iced_widget/ARCADIA-PATCH.md

@@ -0,0 +1,31 @@
+# Pinned Iced widget patch
+
+Upstream crate: iced_widget 0.14.2, MIT. Its registry VCS record identifies
+`iced-rs/iced` commit `54abf81d13fec06d4d9ac754b03ce2c3313e8a1f`, path `widget`.
+The accompanying LICENSE was obtained from that exact upstream commit:
+https://raw.githubusercontent.com/iced-rs/iced/54abf81d13fec06d4d9ac754b03ce2c3313e8a1f/LICENSE
+SHA-256 `fc9086ba4eba4b77e4c603906362742bc3715ffa2c7810c6074fe7780d3a0398`.
+
+All copied src/assets and Cargo manifests retain their upstream bytes except
+`src/text_editor.rs`, which adds one documented read-only `Content::with_editor`
+callback. Original file SHA-256:
+`cecf8686c90aa92066d55075beba545dfb7dd5a44bad0c1519fcb110a56070e1`.
+The callback borrows the existing renderer editor and releases the borrow when
+the closure returns. It adds no mutable editor access or event behavior.
+
+ARCADIA uses this seam to project source diagnostics onto the actual painted
+editor layout. It must not clone/rebuild Content or move user selection for
+measurement. The isolated Windows CPU experiment verified the exact painted
+editor identity and geometry plus retained Word/Line selection and scroll;
+application integration/native validation are separately required.
+
+UPSTREAM-MANIFEST.json records all files from the local pinned registry source,
+including registry bookkeeping and the upstream crate lockfile not copied here.
+Those omitted files are not package inputs. The workspace root Cargo.lock and
+local patch path identify the resolved dependency; this patched package is not
+the unmodified registry checksum. Keep LICENSE and this provenance in source
+captures and generated dependency notices.
+
+On upgrades compare the pristine upstream module and replay only this accessor.
+Recheck actual editor layout, selection/input continuity and annotation tests.
+Remove this patch if upstream provides equivalent read-only layout access.