ci: add PR comment with build artifact download links

On pull requests, after all platform builds complete, post a comment
with a table of artifact names, sizes, and download links. Updates
the same comment on subsequent pushes to the PR (uses HTML marker to
find existing comment). Follows the same pattern as sqlui-native.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: synle

.github/workflows/build.yml

@@ -104,3 +104,59 @@ jobs:
             src-tauri/target/${{ matrix.target }}/release/bundle/rpm/*.rpm
           compression-level: 9
           if-no-files-found: ignore
+
+  # Post a comment on PRs with download links for each platform's build artifacts
+  pr_comment:
+    if: github.event_name == 'pull_request'
+    needs: [build]
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+    steps:
+      - name: Post artifact links on PR
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const runUrl = `https://github.com/${context.repo.owner}/${context.repo.repo}/actions/runs/${context.runId}`;
+            const artifacts = await github.rest.actions.listWorkflowRunArtifacts({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              run_id: context.runId,
+            });
+            let body = `## Build Artifacts\n\n`;
+            if (artifacts.data.artifacts.length === 0) {
+              body += `No artifacts were produced.\n`;
+            } else {
+              body += `| Platform | Size | Download |\n|----------|------|----------|\n`;
+              for (const a of artifacts.data.artifacts) {
+                const sizeMB = (a.size_in_bytes / 1024 / 1024).toFixed(1);
+                const downloadUrl = `${runUrl}/artifacts/${a.id}`;
+                body += `| ${a.name} | ${sizeMB} MB | [Download](${downloadUrl}) |\n`;
+              }
+            }
+            body += `\n[View full run](${runUrl})`;
+
+            // Find and update existing comment or create new one
+            const marker = '<!-- build-artifacts -->';
+            body = marker + '\n' + body;
+            const { data: comments } = await github.rest.issues.listComments({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+            });
+            const existing = comments.find(c => c.body.includes(marker));
+            if (existing) {
+              await github.rest.issues.updateComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                comment_id: existing.id,
+                body,
+              });
+            } else {
+              await github.rest.issues.createComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: context.issue.number,
+                body,
+              });
+            }