feat(cargo): dependency version inspections and updates (#684)

Cargo.toml had no way to tell that a dependency had a newer release.

Dependencies in [dependencies], [dev-dependencies], [build-dependencies], target tables and [workspace.dependencies] now get a weak warning when the newest stable release is outside the version requirement, with a quick fix that rewrites the requirement at its original precision ("0.7" → "0.10") in both string and inline-table forms. Versions complete inside the version string, newest first, without yanked releases. Path, git and workspace-inherited dependencies are skipped, prereleases are only suggested to prerelease requirements, and failures stay silent.

Versions come from the crates.io sparse index through the backend's HTTP client, with an in-memory and on-disk cache and coalesced requests, behind a dependency version source shared by file-type parsers so other manifests can be added later. semver is now used directly; it was already linked into the app.

Fixes #479

src/editor/api.ts

@@ -21,6 +21,7 @@ import {
   Annotation,
   Compartment,
   Facet,
+  StateEffect,
   type EditorState,
   type Extension,
   type RangeSet,
@@ -332,14 +333,25 @@ export function contributedAt<T>(state: EditorState, key: string, pos: number):
   return state.languageDataAt<T>(key, pos)[0];
 }
 
-/** A context action a feature offers at the caret, listed by Show Context Actions (⌥↵) before the language server's. */
+/** A context action a feature offers at the caret, listed by Show Context Actions (⌥↵). */
 export interface ContributedIntention {
   id: string;
   label: string;
   icon?: string;
+  quickFix?: boolean;
   run: () => void | Promise<void>;
 }
 
+/** A background provider has new context actions for the current document. */
+export const intentionsChanged = StateEffect.define<null>();
+
+/** Local fixes of a diagnostic range (hover link and Apply Quick Fix). */
+export const quickFixProviders = Facet.define<(view: EditorView, from: number, to: number) => ContributedIntention[]>();
+
+export function contributedQuickFixes(view: EditorView, from: number, to: number): ContributedIntention[] {
+  return view.state.facet(quickFixProviders).flatMap((provider) => provider(view, from, to));
+}
+
 /** Providers of `ContributedIntention`s for the caret of `view` (cheap and synchronous: also drives the light bulb). */
 export const intentionProviders = Facet.define<(view: EditorView) => ContributedIntention[]>();