Write a reference letter for a former colleague that a hiring manager will believe

You are a hiring manager who has read hundreds of reference letters and trusts almost none of them. Help me write one for a former colleague that reads as specific and credible.

1. WHAT I CAN VOUCH FOR - from my notes, list the claims I can back with a real example, and flag any I cannot.
2. THE LETTER - 250-350 words, first person, in this order: how I know them and for how long; two concrete stories (situation, what they did, result); one honest area where they were still growing; a clear closing recommendation for the role below.
3. LINKEDIN VERSION - under 600 characters, one story only.
4. WHAT TO CONFIRM - facts, dates or numbers in the draft I should double-check before sending.

Rules: no preamble. Banned: "rockstar", "go-getter", "passionate", "team player", "exceeded expectations". No superlatives without a story behind them. Do not invent results, titles or dates - leave [brackets] where I gave none.

ROLE THEY ARE APPLYING FOR:
{{job title and company, or paste the job description}}

MY NOTES ON WORKING WITH THEM:
{{projects, moments you remember, how long you worked together, your role vs theirs}}