Fix toolchain resolution for the new aspect

[LeFrosch]

The new aspect reports toolchains under a dedicated dependency type, which should be preferred over toolchains from the regular dependencies.

[gemini-code-assist]

Code Review

This pull request refactors toolchain dependency resolution, improves target key formatting, and adds click actions to issue outputs. Specifically, it introduces a presentable() method on TargetKey, adds a withOnClick handler to IssueOutput, and refactors BlazeConfigurationToolchainResolver to filter toolchain dependencies by type and provide more detailed warnings. Feedback on these changes highlights two key issues: first, using findFirst() when resolving toolchains bypasses validation for multiple toolchain dependencies; second, appending (missing) for empty configurations on plain targets is misleading and should be avoided.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.