fix(cargo): show clippy error details in compact output

[TechWizard9999]

Description

rtk cargo clippy could collapse output to counts/rules while hiding actionable error text in some failure modes. This PR preserves concise output but always includes concrete error lines.

Related Issue

Closes #602

Changes Made

• enhanced clippy filter to collect and show error detail lines in compact output
• added an Error details section (up to 5 entries, with overflow summary)
• added regression test to ensure error text is present when clippy reports an error
• added changelog entry under Unreleased bug fixes

Files Changed

• src/cargo_cmd.rs - clippy filter enhancement + regression test
• CHANGELOG.md - unreleased bug-fix note for Output filtering hides actual Clippy error messages, only shows summary #602

Testing

• cargo fmt --all --check
• rtk cargo clippy --all-targets (2 pre-existing warnings in untouched files)
• rtk cargo test
• rtk cargo test cargo_cmd::tests::test_filter_cargo_clippy_includes_error_details

Checklist

• Code follows project style guidelines
• Self-review completed
• Documentation updated
• No breaking changes introduced

cc @pszymkowiak for review

[CLAassistant]

All committers have signed the CLA.

[TechWizard9999]

@pszymkowiak could you please review this and let me know if anything needs to change?

[aeppling]

Hey

We are cleaning up the codebase and improving the project structure for better onboarding. As part of this effort, PR #826 reorganizes src/ from a flat layout into subfolders.

No logic changes — only file moves and import path updates.

What you need to do

Rebase your branch on develop when receiving this comment:

git fetch origin && git rebase origin/develop

Git detects renames automatically. If you get import conflicts, update the paths:

use crate::git;        // now: use crate::cmds::git::git;
use crate::tracking;   // now: use crate::core::tracking;
use crate::config;     // now: use crate::core::config;
use crate::init;       // now: use crate::hooks::init;
use crate::gain;       // now: use crate::analytics::gain;

Need help rebasing? Tag @aeppling

[TechWizard9999]

Rebased on latest develop per the refactor notice and force-updated this branch.

@pszymkowiak could you please re-review when convenient?