Improve relative datetime parsing

[itssimon]

Summary by cubic

Extend resolve_relative_datetime to parse simple ISO 8601-style durations (e.g., P14D, -P14D, PT24H, PT30M) in addition to compact forms like 24h, returning the UTC instant that far in the past as RFC 3339. Inputs that don’t match are left unchanged, and tests cover the new formats and case-insensitive handling.

^{Written for commit 5d68b1d. Summary will update on new commits.}

[sentry]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.23%. Comparing base (408dc37) to head (5d68b1d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #27      +/-   ##
==========================================
+ Coverage   91.20%   91.23%   +0.03%     
==========================================
  Files          12       12              
  Lines        2057     2066       +9     
==========================================
+ Hits         1876     1885       +9     
  Misses        181      181              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[cubic-dev-ai]

No issues found across 1 file