feat(github): pull request tool window, timeline and review flow (#477)

Replaces the Pull Requests tool window with a full review workflow on top of gh's authentication.

- List with search, quick filters and paging; a tab per pull request and a New Pull Request tab.
- Details: commit picker, changes tree with viewed state, CI and reviewer status, merge, close and reopen.
- Timeline editor: comments, review threads, reactions and suggested changes.
- Review in the diff viewer and, for the checked-out branch, in the editor (review mode).
- New generic vcs extension points: registerDiffViewerProvider, lineInlays, reviewGutter, branch widget extensions; new vcs_merge_base and gh_api commands.
- CSP: img-src allows https://avatars.githubusercontent.com for avatars.

Fixed while testing against a real repository: remotes behind an SSH host alias, mergeability stuck on UNKNOWN, Apply Locally staying disabled after a checkout, relative links navigating the app's page, and review inlays wider than the pane.

Co-authored-by: imacross <[email protected]>

src-tauri/src/commands/github.rs

@@ -3,7 +3,7 @@
 use crate::state::AppState;
 use ide_core::{IdeError, IdeResult, RequestId};
 use ide_github::{
-    CreatePullRequest, GhAvailability, PrDiffRevisions, PrListQuery, PrReviewComment, PullRequestDetails,
+    CreatePullRequest, GhApiRequest, GhAvailability, PrDiffRevisions, PrListQuery, PrReviewComment, PullRequestDetails,
     PullRequestSummary, ReviewEvent,
 };
 use std::path::PathBuf;
@@ -128,6 +128,14 @@ pub async fn gh_pr_comment(window: Window, state: State<'_, AppState>, number: u
     blocking(move || ide_github::add_comment(&root, number, &body)).await
 }
 
+/// A GitHub GraphQL / REST call through `gh api`; returns the response body.
+#[tauri::command]
+#[specta::specta]
+pub async fn gh_api(window: Window, state: State<'_, AppState>, request: GhApiRequest) -> IdeResult<String> {
+    let root = root(&window, &state)?;
+    blocking(move || ide_github::api(&root, &request)).await
+}
+
 /// Fetches what is missing to diff a pull request locally; returns the revisions to compare.
 #[tauri::command]
 #[specta::specta]