fix(RateChangeQueue): empty queue behavior

[wjmelements]

Fixes #266
Reviewer @ZenGround0

Changes

• move reset of head = 0 to when zeroing rail
• change string revert error 'Queue is empty' into abi 'error EmptyQueue()'
• remove redundant bounds checking with unchecked

[ZenGround0]

I just beat you to posting the PR and I kind of like my/claude's solution better ( https://github.com/FilOzone/filecoin-pay/pull/269/changes) but I'm happy to talk about it more.

[wjmelements]

The test failure is unrelated and was broken in a dependency. I will try to fix it in a separate PR.

Run forge coverage --report lcov --ir-minimum
  forge coverage --report lcov --ir-minimum
  shell: /usr/bin/bash -e {0}
  env:
    FOUNDRY_PROFILE: ci
Warning: This is a nightly build of Foundry. It is recommended to use the latest stable version. To mute this warning set `FOUNDRY_DISABLE_NIGHTLY_WARNING` in your environment. 

Error: failed to extract foundry config:
foundry config error: selected profile `ci` does not exist
Error: Process completed with exit code 1.

[ZenGround0]

Looks like we could take the last two bullet points as nice add ons in addition to PR #269

[wjmelements]

I just beat you to posting the PR and I kind of like my/claude's solution better ( https://github.com/FilOzone/filecoin-pay/pull/269/changes) but I'm happy to talk about it more.

Discuss on the other issue: #266 (comment)

[wjmelements]

The test failure is unrelated and was broken in a dependency. I will try to fix it in a separate PR.

Run forge coverage --report lcov --ir-minimum
  forge coverage --report lcov --ir-minimum
  shell: /usr/bin/bash -e {0}
  env:
    FOUNDRY_PROFILE: ci
Warning: This is a nightly build of Foundry. It is recommended to use the latest stable version. To mute this warning set `FOUNDRY_DISABLE_NIGHTLY_WARNING` in your environment. 

Error: failed to extract foundry config:
foundry config error: selected profile `ci` does not exist
Error: Process completed with exit code 1.

#273

[codecov]

Codecov Report

❌ Patch coverage is 73.33333% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/RateChangeQueue.sol	71.42%	4 Missing ⚠️

❌ Your patch check has failed because the patch coverage (73.33%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

@@           Coverage Diff           @@
##             main     #272   +/-   ##
=======================================
  Coverage        ?   76.99%           
=======================================
  Files           ?        5           
  Lines           ?      539           
  Branches        ?      104           
=======================================
  Hits            ?      415           
  Misses          ?      120           
  Partials        ?        4           

Flag	Coverage Δ
foundry	76.99% <73.33%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/FilecoinPayV1.sol	83.22% <100.00%> (ø)
src/RateChangeQueue.sol	80.95% <71.42%> (ø)

🚀 New features to boost your workflow:

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[wjmelements]

Regretfully I updated my forge to 1.5.1 and now I cannot downgrade to 1.3.5. I have tried foundryup -C 9979a41b5daa5da1572d973d7ac5a3dd2afc0221

[wjmelements]

I have reviewed the lines codecov thinks are missing test coverage. They all have test coverage. Likely related to via-ir.