Normalize copilot-session-insights discussion output hierarchy and disclosure

[Copilot]

copilot-session-insights.md produced discussion bodies with #/## headings and lacked explicit structure guidance for collapsible detail sections. This update aligns the workflow with reporting conventions used by other workflows: enforce h3+ headings and apply progressive disclosure for verbose analysis blocks.

• Formatting contract added near Phase 5

  • Introduced a new ### Report Formatting section that explicitly requires:
    • h3 (###) or lower headings in discussion bodies (no h1/h2)
    • <details><summary><b>…</b></summary> for long sections
    • always-visible Executive Summary, Key Metrics, and Recommendations

• Discussion template heading hierarchy normalized

  • Demoted template headings from #/## (and downstream levels) to ###/####/##### to keep issue/discussion body hierarchy compliant.

• Progressive disclosure added to verbose report sections

  • Wrapped high-volume sections in <details> blocks, including:
    • per-prompt quality breakdown
    • orphaned branch escalation candidate details
    • loop/tool/context diagnostic breakdown
    • historical trends + statistical summary

Example of the updated template pattern:

### 🤖 Copilot Agent Session Analysis — [DATE]

#### Executive Summary
...

<details>
<summary><b>Per-Prompt Breakdown</b></summary>

##### High-Quality Prompt Characteristics
...
##### Low-Quality Prompt Characteristics
...

</details>

[Copilot]

Pull request overview

Updates the copilot-session-insights discussion template to enforce a consistent heading hierarchy (h3+) and introduce progressive disclosure for verbose report sections, matching formatting conventions used by other reporting workflows.

Changes:

• Added an explicit “Report Formatting” contract requiring h3+ headings in discussion bodies and using <details> blocks for long sections.
• Normalized the discussion template headings from #/## to ###/####/#####.
• Wrapped high-volume template sections (per-prompt breakdown, escalation candidate details, diagnostics, trends/statistics) in collapsible <details> sections.

Show a summary per file

File	Description
.github/workflows/copilot-session-insights.md	Adds formatting requirements and restructures the discussion template to use h3+ headings plus <details>-based progressive disclosure.

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