fix: firstCommitAt calculation

[waltergalvao]

Summary by CodeRabbit

• Bug Fixes

  • More accurate cycle time and time-to-code calculations, including cases where commits are dated before PR creation (rebases/edge cases).

• Refactor

  • Improved commit date tracking using author/committer date fallbacks and preserving the earliest observed commit date across updates.

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[coderabbitai]

Walkthrough

Renames getCycleTime parameter from firstCommitAt to fromDate and updates PR tracking to compute a preserved earliest firstCommitAt, derive startedCodingAt, and recompute timeToCode and cycleTime using the appropriate anchor between first commit and PR creation.

Changes

Cohort / File(s)	Summary
Parameter rename apps/api/src/app/github/services/github-pull-request-tracking.service.ts	Renamed getCycleTime second parameter from firstCommitAt to fromDate and updated internal null-checks and usage in differenceInBusinessMilliseconds.
Cycle time & first-commit preservation apps/api/src/app/github/services/github-pull-request.service.ts	Adds candidateFirstCommitAt (author.date fallback to committer.date); preserves earliest firstCommitAt across observations; computes startedCodingAt as earlier of firstCommitAt and PR creation; recomputes timeToCode and cycleTime; minor GraphQL formatting tweaks.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• fix: merge commit SHA for revert PRs #66: Modifies upsertPullRequest in the same service—overlaps in how PR fields (e.g., first commit / merge commit) are derived and stored.

Suggested labels

medium

Suggested reviewers

• sweetrdev

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: a fix to the firstCommitAt calculation logic, which is the core functional change across both modified files.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

• 📝 Generate docstrings

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@apps/api/src/app/github/services/github-pull-request.service.ts`:
- Around line 331-356: The computed timeToCode currently uses
tracking?.firstReadyAt (stale/missing) instead of the freshly computed
firstReadyAt; update the call to getTimeToCode to pass the newly computed
firstReadyAt (with a fallback to tracking.firstReadyAt if needed) so timeToCode
= getTimeToCode(firstCommitAt, firstReadyAt ?? tracking?.firstReadyAt) (locate
symbols: firstCommitAt, firstReadyAt, tracking, getTimeToCode, timeToCode) and
ensure the rest of the logic still falls back correctly when no ready date
exists.