data: add Cyber Chief startup program

[zmx2013]

What changed

Adds Cyber Chief and its current Cyber Chief Startup Program as one consolidated startup offer.

The record captures:

• 75% off a Cyber Chief subscription during the first program year
• 35% off during the second program year
• The published Startup or Growth package applicability for the first-year discount
• Published eligibility requiring the applicant to be a new Cyber Chief client that is not currently and has not previously been a paid client, have raised less than US$5 million, and have raised Pre-Seed, Seed, or Series A funding from a recognised fund or investor
• The public first-party Startup Program application form

The change is data-only and adds exactly one file:

vendors/cy/cyber-chief.yaml

Closes #767

Sources

• https://www.cyberchief.ai/p/application-security-tool-for-startups.html
• https://start.cyberchief.ai/apply

Certification

• I changed only allowed repository content and did not mix vendor YAML with other paths.
• Public sources substantiate every submitted factual value; any Sourcey-written prose is a neutral summary, not a fabricated vendor quote.
• I did not author verification, provenance, freshness, or signature claims.
• My commits include a Signed-off-by line.