docs: add investigation for new-user activation drop after signup credit removal

[kilo-code-bot]

Summary

• Corrects the investigation timeline for the new-user activation drop after signup credit removal
• Key correction: commit 831f1b2f was never merged to main — it existed only on branch remove-free-5-signup-credit in PR feat(credits): remove free $5 credit for new users #928, which was closed without merging on 2026-03-09 09:16:19 UTC
• The credit was disabled on main only when PR feat(credits): remove free $5 credit for new users #940 (from branch mark/remove-free-5-signup-credit with re-authored commits) was merged on 2026-03-11 at 14:02:54 UTC
• The previous version of this document incorrectly stated the credit was "disabled on March 9" — it was not deployed to main until March 11

Verification

• git merge-base --is-ancestor 831f1b2f main returns exit code 1 (not an ancestor of main)
• git branch -a --contains 831f1b2f shows only remotes/origin/remove-free-5-signup-credit
• gh pr view 928 confirms PR was closed without merging on 2026-03-09 09:16:19 UTC
• gh pr view 940 confirms PR was merged on 2026-03-11 14:02:54 UTC with merge commit 47d0cc2d
• git show --format=fuller on all relevant commits confirmed exact timestamps

Visual Changes

N/A

Reviewer Notes

The original document implied commit 831f1b2f disabled the credit on main on March 9, which could lead to incorrect root cause analysis timing. The credit was only removed from main on March 11 via PR #940. This is a meaningful correction if the activation drop timeline is being correlated with deployment dates.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (1 files)

• docs/investigations/2026-03-13-activation-drop-signup-credit.md

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_{Reviewed by gpt-5.4-20260305 · 95,655 tokens}