fix(workflow): normalize report formatting in prompt-clustering-analysis (#21915)

* Initial plan

* fix: normalize report formatting in prompt-clustering-analysis workflow

- Remove H1 header from report template body (title goes in title field)
- Downgrade H2 (##) to H3 (###) for all section headers
- Update cluster sub-headers from ### to #### (nested under ### Cluster Analysis)
- Add bold formatting to <summary> tag: <summary><b>Full Analysis Report</b></summary>

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
Agent-Logs-Url: https://github.com/github/gh-aw/sessions/26cf2ac6-cde8-4a6e-a4b1-2953a960ce77

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
Co-authored-by: Peli de Halleux <pelikhan@users.noreply.github.com>

Author: Copilot

.github/workflows/prompt-clustering-analysis.md

@@ -488,30 +488,26 @@ Create a comprehensive discussion report with:
 **Report Template**:
 
 ```markdown
-# 🔬 Copilot Agent Prompt Clustering Analysis - [DATE]
-
-Daily NLP-based clustering analysis of copilot agent task prompts.
-
-## Summary
+### Summary
 
 **Analysis Period**: Last 30 days
 **Total Tasks Analyzed**: [count]
 **Clusters Identified**: [count]
 **Overall Success Rate**: [percentage]%
 
 <details>
-<summary>Full Analysis Report</summary>
+<summary><b>Full Analysis Report</b></summary>
 
-## General Insights
+### General Insights
 
 - **Most Common Task Type**: [cluster description]
 - **Highest Success Rate**: [cluster with best success rate]
 - **Most Complex Tasks**: [cluster with most turns/highest complexity]
 - **Outliers**: [number of outlier tasks identified]
 
-## Cluster Analysis
+### Cluster Analysis
 
-### Cluster 1: [Theme/Description]
+#### Cluster 1: [Theme/Description]
 - **Size**: X tasks ([percentage]% of total)
 - **Success Rate**: [percentage]%
 - **Average Turns**: [number]
@@ -523,32 +519,32 @@ Daily NLP-based clustering analysis of copilot agent task prompts.
 
 ---
 
-### Cluster 2: [Theme/Description]
+#### Cluster 2: [Theme/Description]
 ...
 
-## Success Rate by Cluster
+### Success Rate by Cluster
 
 | Cluster | Tasks | Success Rate | Avg Turns | Top Keywords |
 |---------|-------|--------------|-----------|--------------|
 | 1       | 15    | 87%          | 3.2       | refactor, cleanup |
 | 2       | 12    | 75%          | 4.1       | bug, fix, error |
 | 3       | 8     | 100%         | 2.5       | docs, update |
 
-## Full Data Table
+### Full Data Table
 
 | PR # | Title | Cluster | Outcome | Turns | Keywords |
 |------|-------|---------|---------|-------|----------|
 | 123  | Fix bug in parser | 2 | Merged | 4 | bug, fix, parser |
 | 124  | Update docs | 3 | Merged | 2 | docs, update |
 | 125  | Refactor logger | 1 | Merged | 3 | refactor, logger |
 
-## Key Findings
+### Key Findings
 
 1. **[Finding 1]**: [Description and data supporting this finding]
 2. **[Finding 2]**: [Description and data supporting this finding]
 3. **[Finding 3]**: [Description and data supporting this finding]
 
-## Recommendations
+### Recommendations
 
 Based on clustering analysis: