content(tools): add iconUrl for hyperline, outreach, vitally

[wab]

Three tool entries have no iconUrl in their frontmatter:

• tools/hyperline.md
• tools/outreach.md
• tools/vitally.md

Pre-existing gap surfaced during the blob store migration (PR #48) when we audited tool icons. Other tools all reference iconUrl: https://ipjmp3k0z0p479cb.public.blob.vercel-storage.com/content/tools/<slug>.<ext>.

Why human, not agent

We need a human to source the official icons (vendor brand assets, correct format/dimensions, licensing OK). Once sourced:

1. Drop the icon at assets/tools/<slug>.svg (or .png / .jpeg)
2. pnpm upload-assets:migrate to push to the new store
3. Add iconUrl: https://ipjmp3k0z0p479cb.public.blob.vercel-storage.com/content/tools/<slug>.<ext> to the markdown frontmatter

Acceptance

All 3 tool detail pages render with an icon on the consuming website.

[wab]

This was generated by AI during triage.

Surfaced during PR #48's tool-icon migration — tools/hyperline.md, tools/outreach.md, tools/vitally.md have no iconUrl frontmatter. Pre-existing gap, not introduced by the migration.

My recommendation: enhancement + ready-for-human. Reason: requires a human to source vendor brand assets (licensing, dimensions, format). Once icons exist locally, the upload + frontmatter edit is mechanical.

Could also be argued as bug if the rendering site breaks on missing iconUrl — worth checking before grilling.