Fix forest-wallet set-default failing when the keystore has no default entry

[sudo-shashank]

Summary of changes

Changes introduced in this pull request:

• Fixed and unified set-default logic by adding a check for an existing default entry before removing it.

Reference issue to close (if applicable)

Closes #7018

Other information and links

Change checklist

• I have performed a self-review of my own code,
• I have made corresponding changes to the documentation. All new code adheres to the team's documentation standards,
• I have added tests that prove my fix is effective or that my feature works (if possible),
• I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.

Outside contributions

• I have read and agree to the CONTRIBUTING document.
• I have read and agree to the AI Policy document. I understand that failure to comply with the guidelines will lead to rejection of the pull request.

Summary by CodeRabbit

• Bug Fixes

  • forest-wallet set-default command now handles cases where the keystore lacks a default entry, resolving issue #7018.

• Refactor

  • Improved consistency and maintainability of wallet default key management code across wallet operations and RPC handlers.

[coderabbitai]

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The changes directly address issue #7018 by refactoring the set-default logic to handle cases where no existing default entry exists.
Out of Scope Changes check	✅ Passed	All changes are scoped to fixing the set-default functionality and include a changelog update, with no unrelated modifications present.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title accurately and specifically describes the main change: fixing the forest-wallet set-default command to handle keystores without a default entry, which directly aligns with the changeset's objective of resolving issue #7018.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch shashank/fix-wallet-set-default

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch shashank/fix-wallet-set-default

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[codecov]

Codecov Report

❌ Patch coverage is 45.45455% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.23%. Comparing base (3b7dcd7) to head (0f0089d).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/key_management/wallet.rs	55.55%	1 Missing and 3 partials ⚠️
src/rpc/methods/wallet.rs	0.00%	1 Missing ⚠️
src/wallet/subcommands/wallet_cmd.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
src/rpc/methods/wallet.rs	35.46% <0.00%> (+0.80%)	⬆️
src/wallet/subcommands/wallet_cmd.rs	26.68% <0.00%> (+0.19%)	⬆️
src/key_management/wallet.rs	90.00% <55.55%> (+0.08%)	⬆️

... and 9 files with indirect coverage changes

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[LesnyRumcajs]

why does this need to be a free function?

[sudo-shashank]

matches other methods in this module like get_default, list_addrs, remove_key etc

[LesnyRumcajs]

This isn't a compelling argument; this is essentially a method on the keystore that requires the keystore. I think what you should consider is moving the listed methods under the aegis of keystore. Rust is a multi-paradigm language, OOP (or parts of it) being on them. Entities like keystore would benefit well from proper encapsulation.