team: add Brianna Gabaldon as an advisor

[yorkerhodes3]

What

Adds Brianna Gabaldon - Product Manager at Microsoft and an NYU CGA alum - to team.advisors in src/content/site.ts, following the procedure in .github/skills/add-team-profile/SKILL.md (merged in #48).

• Role: "Advisor" - kept plain, no dot-separated focus area, per direct request (other advisors follow "Advisor · <focus>", but that pattern was explicitly declined here).
• Org: "Product Manager, Microsoft · NYU CGA alum"
• LinkedIn: the URL supplied.
• Bio: the description supplied, lightly extended into a full sentence to match the third-person style of the other advisor bios: "Brianna Gabaldon is a Product Manager at Microsoft and an alum of NYU's Center for Global Affairs. Her work sits at the intersection of one of the most scaled-up user experiences in the world and the human condition."
• Slug: brianna-gabaldon - checked against every existing slug across all categories, no collision.

The headshot

Supplied as a PNG screenshot/photo. Converted to JPEG before adding: it's a photograph with a busy background, not a flat mark, so lossless PNG couldn't get it under the 90KB team-photo budget even resized to the 384px cap - optimize:images still reported ~310KB. As a JPEG it resizes to 15KB, in line with every other headshot in public/team/.

public/team/README.md intentionally not updated - its status list only tracks the founder and current-cohort researchers; advisors (Teresa, Sylvia) were never listed there either, so adding Brianna would have broken that existing convention rather than followed it.

Verified

• No slug collision against the full roster (founder, advisors, staff, researchers, collaborators).
• check:content and check:images both pass - as expected, since the cohort-count invariant only applies to researchers, not advisors.
• Lint, typecheck, and build pass.
• Inspected the built HTML directly: her card renders correctly on /team (photo, name, link to detail page), and /team/brianna-gabaldon renders name, role, org, LinkedIn link, and bio correctly.
• Snapshot integrity: 87 pages, 6,873 asset/photo references, 0 missing. Only 13 files changed in the snapshot commit (her new page + photo + the pages that link to her) - no unrelated churn.