fix(skills): add YAML frontmatter delimiters to 29 SKILL.md files

[mkhalif-xyz]

Summary

• 29 SKILL.md files across private-equity, equity-research, investment-banking, and wealth-management ship without YAML frontmatter delimiters. The files start with a Markdown heading followed by a literal `description:` line in the body, so Claude Code cannot reliably index `name`/`description` and the skills don't auto-trigger.
• This PR wraps the existing name (derived from the directory) and description in proper `---` delimiters and removes the in-body description line. No semantic content changes.
• `scripts/sync-agent-skills.py` propagated the fix into 12 bundled copies under `agent-plugins/`, and `scripts/check.py` passes (was failing on 12 drift issues prior).

Affected verticals

• private-equity (10): ai-readiness, dd-checklist, dd-meeting-prep, deal-screening, deal-sourcing, ic-memo, portfolio-monitoring, returns-analysis, unit-economics, value-creation-plan
• equity-research (7): catalyst-calendar, earnings-preview, idea-generation, model-update, morning-note, sector-overview, thesis-tracker
• investment-banking (6): buyer-list, cim-builder, deal-tracker, merger-model, process-letter, teaser
• wealth-management (6): client-report, client-review, financial-plan, investment-proposal, portfolio-rebalance, tax-loss-harvesting

Before / after

Before (e.g. `private-equity/skills/ic-memo/SKILL.md`):
```

Investment Committee Memo

description: Draft a structured investment committee memo for PE deal approval...
```

After:
```

name: ic-memo
description: "Draft a structured investment committee memo for PE deal approval..."

Investment Committee Memo

```

Test plan

• All 29 source SKILL.md files now start with valid YAML frontmatter delimiters
• `python3 scripts/sync-agent-skills.py` updated 12 bundled copies under `agent-plugins/`
• `python3 scripts/check.py` passes (0 issues across 80 files)
• Reviewer to verify the rewritten descriptions auto-trigger as expected in Claude Code

🤖 Generated with Claude Code