fix: advance FixedWindowCallRatePolicy windows past all elapsed periods

[devin-ai-integration]

Summary

👉 TL;DR: Fixed-window rate limiting could stop enforcing its call limit after the limiter sat idle across several windows, and rejected calls made at the exact instant a window reset. Specifically, FixedWindowCallRatePolicy._update_current_window now rolls forward across every elapsed period at once and treats now == _next_reset_ts as the start of the new window.

Resolves https://github.com/airbytehq/airbyte-internal-issues/issues/17245:

• https://github.com/airbytehq/airbyte-internal-issues/issues/17245

Related open PRs touching the same class (not merged/conflicting in scope): #985, #989.

Changes

• _update_current_window: on rollover, compute elapsed_periods = (now - _next_reset_ts) // _offset + 1 and advance _next_reset_ts by that many periods, so alignment is preserved and the pointer lands strictly after now. Previously it advanced by exactly one period per call, so after N missed periods the next N try_acquire calls each reset _calls_num to 0 and the limit was never enforced.
• Rollover condition changed from now > _next_reset_ts to now >= _next_reset_ts, so a call at the exact reset instant is admitted instead of raising CallRateLimitHit with next reset in 0:00:00.
• Behavior when fewer than one period has elapsed is unchanged.
• create_fixed_window_call_rate_policy in the declarative factory is intentionally not touched.

Risks

• Practically, the missed-period bug is most visible after update() sets _next_reset_ts from API headers to a time in the past; the factory seeds it 10 days ahead. Behavior change is strictly toward enforcing the configured limit.

Test plan

• New tests in unit_tests/sources/streams/test_call_rate.py::TestFixedWindowCallRatePolicy (freezegun): multiple missed periods enforce the limit; call allowed exactly at reset boundary; alignment preserved after skipping periods; single-period rollover. The first two fail on main and pass on this branch.
• poetry run pytest unit_tests/sources/streams/test_call_rate.py -q — 42 passed
• poetry run ruff check ., poetry run ruff format ., poetry run mypy --config-file mypy.ini airbyte_cdk/sources/streams/call_rate.py — clean

Requested via the /ai-fix workflow on the linked issue.

Link to Devin session: https://app.devin.ai/sessions/7d579e79131e44118d81355f44a6b2c6
Open in Devin Desktop: https://app.devin.ai/desktop/session/7d579e79131e44118d81355f44a6b2c6?variant=devin

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[github-actions]

PyTest Results (Fast)

4 392 tests  +4   4 380 ✅ +4   9m 41s ⏱️ +3s
    1 suites ±0      12 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit 08916a3. ± Comparison against base commit 96a7c0a.

[github-actions]

PyTest Results (Full)

4 395 tests  +4   4 383 ✅ +4   13m 22s ⏱️ -39s
    1 suites ±0      12 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit 08916a3. ± Comparison against base commit 96a7c0a.