test(aws): preserve requested-window SP coverage rates

[cristim]

Savings Plans hourly rates normalize reported totals over the requested window. Counting only returned coverage blocks would inflate rates for valid sparse usage: 240USD across a 30-day window is 1/3USD/hour whether 20 inactive days are omitted or explicitly zero.

Add the sparse/explicit-zero/nil regression, including pagination, and clarify the exported rate and Days comments. No production calculation changes. Refs #51, specifically the independently reviewed A07-019 disposition. Reporting completeness cannot be inferred from this endpoint's missing days.

Issue #51 remains open while the separate RI fix in #167 and the reporting-completeness disposition are completed. The recorded semantic decision retains the full-window divisor. The fixture cannot establish whether an omitted live period means zero activity or delayed reporting; no new live incomplete-data defect is claimed.

Verification: recommendations race suite, AWS build, pinned lint2.10.1 and normal hooks pass. An intentional Days-based divisor mutation fails the new regression at 1 versus 1/3USD/hour. A real AWS SDK/local HTTP fixture confirms equal requested-window rates for sparse and explicit-zero responses; no live AWS calls.

Independent gpt-6-astra review approved final integrated commit cd4aa1286951dbf70e0b1ba413c7a61b0349291c: clean checkout and parent verification, full main-relative diff reread, GCP files identical to main 28efbcd, fresh AWS RI/SP and GCP consumer race tests, and real SDK/local HTTP experiment. Additive merges preserve the original SP commit 19dba433cc6db5b63978b2b14dfe5b2c81fcc96d; the SP contract files are unchanged. The reviewer independently confirmed that the Days-based mutation fails the intended rate assertions. Explicit normal hooks on the SP and incoming GCP files passed. This is the user-authorized independent review path; CodeRabbit is optional.

[coderabbitai]

Warning

Review limit reached

• Run on-demand review

_{This review includes 2 billable files and costs up to $0.50.}

• Ask an admin to make reviews automatic

Open in CodeRabbit

Reviews can continue after your included limit without a manual trigger. An admin must approve usage-based billing.

Or wait 10 minutes for your next included review.

Check out review usage here.

View limit details

Limit details: You’ve used the included review currently available. Your 70 included PR review attempts over the past 7 days set your current allowance at 1 review per hour.

Learn how review limits work.

Review configuration:

⚙️ Run configuration

Configuration used: Repository: LeanerCloud/cloud-commitments-go/.coderabbit.yaml

Review profile: CHILL

Plan: Essentials

Run ID: ca5468d9-84c7-44ae-8d8a-554ab9f9416e

📥 Commits

Reviewing files that changed from the base of the PR and between 28efbcd and cd4aa12.

📒 Files selected for processing (2)

• providers/aws/recommendations/sp_coverage.go
• providers/aws/recommendations/sp_coverage_window_test.go

---

_{Comment @coderabbitai help to get the list of available commands.}