perf: run benchmarks daily and deduplicate regression issues (#1871)

* perf: run benchmarks daily and deduplicate regression issues

- Change cron schedule from weekly (Mondays) to daily at 06:00 UTC
- When a regression is detected, check for an existing open issue with
  performance+needs-investigation labels before creating a new one.
  If one exists, comment on it with updated data instead of duplicating.

Closes #1865
Closes #1868

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

* fix: filter out PRs from dedup query and trim update comments

Address Copilot review feedback:
- Filter out pull requests from issues.listForRepo results since the API
  returns both issues and PRs; an open PR with matching labels could be
  mistakenly selected instead of a regression issue.
- Reduce update comment size to a short summary (date, run link, commit,
  regression list) with a link to full artifacts, avoiding potential
  GitHub comment size limits on daily runs.
- Bump per_page from 1 to 5 to account for PRs being filtered out.

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

---------

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

Author: Mossaka

.github/workflows/performance-monitor.yml

@@ -2,8 +2,8 @@ name: Performance Monitor
 
 on:
   schedule:
-    # Run weekly on Mondays at 06:00 UTC
-    - cron: "0 6 * * 1"
+    # Run daily at 06:00 UTC
+    - cron: "0 6 * * *"
   workflow_dispatch:
     inputs:
       iterations:
@@ -165,14 +165,40 @@ jobs:
             ].join('\n');
 
             try {
-              const issue = await github.rest.issues.create({
+              // Check for existing open regression issue to avoid duplicates on daily runs
+              const existing = await github.rest.issues.listForRepo({
                 owner: context.repo.owner,
                 repo: context.repo.repo,
-                title: `Performance regression detected (${new Date().toISOString().split('T')[0]})`,
-                body,
-                labels: ['performance', 'needs-investigation'],
+                labels: 'performance,needs-investigation',
+                state: 'open',
+                per_page: 5,
               });
-              core.info(`Created regression issue: ${issue.data.html_url}`);
+
+              // Filter out PRs (listForRepo returns both issues and PRs)
+              const existingIssues = existing.data.filter(item => !item.pull_request);
+
+              if (existingIssues.length > 0) {
+                // Comment on existing issue with a short summary (link to run for full details)
+                const issueNumber = existingIssues[0].number;
+                const runUrl = `${context.serverUrl}/${context.repo.owner}/${context.repo.repo}/actions/runs/${context.runId}`;
+                const regressionList = report.regressions.map(r => `- ${r}`).join('\n');
+                await github.rest.issues.createComment({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  issue_number: issueNumber,
+                  body: `## Updated Regression Data (${new Date().toISOString().split('T')[0]})\n\n**Run:** [${context.runId}](${runUrl})\n**Commit:** ${report.commitSha}\n\n### Regressions\n${regressionList}\n\nSee the [workflow run](${runUrl}) for full results and artifacts.`,
+                });
+                core.info(`Updated existing regression issue #${issueNumber}`);
+              } else {
+                const issue = await github.rest.issues.create({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  title: `Performance regression detected (${new Date().toISOString().split('T')[0]})`,
+                  body,
+                  labels: ['performance', 'needs-investigation'],
+                });
+                core.info(`Created regression issue: ${issue.data.html_url}`);
+              }
             } catch (error) {
-              core.setFailed(`Failed to create regression issue: ${error.message}`);
+              core.setFailed(`Failed to create/update regression issue: ${error.message}`);
             }