feat: confirm co-founder conditional fields from live form testing

Clicked Add co-founder on real form. Confirmed:
- Invite requires real email (min 10% equity to count as founder)
- "How long have founders known each other + met in person?" appears
  immediately as single combined textbox
- "Interesting project together" likely appears post-invite-acceptance
  (cannot confirm without real co-founder on account)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: thisisfatih

skills/form-fill/SKILL.md

@@ -102,7 +102,9 @@ Repeat for each additional co-founder.
 After returning to main application:
 
 - **"Who writes code, or does other technical work on your product? Was any of it done by a non-founder? Please explain."** - be specific: name the founder(s), what they built, any contractor work
-- **"Are you looking for a cofounder?"** - fill only if actively looking; if team is complete, leave blank or answer appropriately
+- **"Are you looking for a cofounder?"** - fill only if actively looking; leave blank if team is complete
+- **"How long have the founders known one another and how did you meet? Have any of the founders not met in person?"** - appears when a second founder is on the application (confirmed). Single textbox covering all three sub-questions.
+- **"Please tell us about an interesting project or thing you have built or achieved together."** - appears after co-founder accepts invite and completes profile. Include URLs.
 
 After filling:
 - Take screenshot

skills/yc-application/references/application-questions.md

@@ -84,11 +84,18 @@ The technical-founder check. Best answer: a founder wrote everything. If contrac
 ### "Are you looking for a cofounder?"
 Fill if actively seeking. Leave blank or answer "no" if team is complete.
 
-### Co-founder questions (appear when second founder is added)
-When you add a co-founder, additional questions appear:
-- Interesting project two or more of you created together (include URLs - if nothing, that's a gap)
-- How long have the founders known one another and how did you meet?
-- Have any of the founders not met in person?
+### Co-founder questions (appear when second founder slot is opened)
+
+**Confirmed:** "How long have the founders known one another and how did you meet? Have any of the founders not met in person?" - single combined textbox, appears immediately when a second founder is being added.
+
+**Likely appears after co-founder accepts invite and completes profile:** "Please tell us about an interesting project or thing you have built or achieved together." - cannot verify without a real co-founder on the account. Include URLs. If you have nothing built together, that's a gap - address it directly.
+
+**Co-founder invite mechanics:** Adding a co-founder requires a real email. YC sends an invite. The co-founder must accept and complete their own profile. Equity requirement: "To be considered a founder, a person must own at least 10% equity in the company."
+
+Rubric for "how long have you known each other":
+- Long-term friendship + shipped work together = strongest signal
+- Recent introduction = not disqualifying, but the bar on shared shipped work is higher
+- Never met in person = yellow flag. Address when you'll meet.
 
 ---