Add regression test that list_fee_waived_anchors' pagination matches list_anchors' skip-without-counting behavior

[Jagadeeshftw]

📌 Description

list_fee_waived_anchors(start, limit) explicitly mirrors list_anchors's pagination pattern per its own doc comment, additionally filtering on is_fee_waived. There is no existing test confirming the two functions produce consistent, comparable pagination results (e.g. that a start index refers to the same underlying AnchorList position in both, and that both correctly skip non-matching/deregistered entries without consuming limit slots) when run against the identical underlying anchor list.

🧩 Requirements and context

• Add a regression test with a mix of registered, deregistered, waived, and non-waived anchors in AnchorList, then compare list_anchors(start, limit) and list_fee_waived_anchors(start, limit) outputs for consistency with independently-computed expected subsets.
• Cover a start value that lands in the middle of a run of skipped (deregistered or non-waived) entries for both functions.
• Assert both functions never include more than limit entries and never miscount skipped entries toward that limit.

🛠️ Suggested execution

• Add the comparative test to src/test.rs, building a shared anchor-list fixture used by both assertions.
• No production code changes expected — this closes a cross-function consistency test gap.
• Cross-reference the existing 'pagination edge-case regression tests across every list_* entrypoint' issue in this repo's backlog to avoid duplicating its exact scenarios; this issue is specifically about cross-function consistency, not single-function edge cases.

✅ Acceptance criteria

• A regression test confirms list_anchors and list_fee_waived_anchors behave consistently against the same underlying AnchorList fixture.
• Both functions correctly skip non-matching entries without counting them toward limit.
• The test would catch a future divergence between the two functions' pagination semantics.

🔒 Security notes

Divergent pagination semantics between two functions documented as mirroring each other could mislead an off-chain client that assumes identical start/limit behavior, silently dropping or duplicating anchors in a paginated UI.

📋 Guidelines

• Minimum 95% test coverage
• Clear documentation
• Timeframe: 96 hours

[OluRemiFour]

Hi Maintainer,
Interested in working on this issue. I'll implement the requested changes and ensure everything is properly tested before submission.

[grantfox-oss]

🦊 GrantFox — @OluRemiFour has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #147)
2. Your PR will be reviewed by the AnchorNet-Org maintainers

Good luck! Track your progress on GrantFox.