feat(sbt): support anonymous objects and dotted symbols for version declaration

[Thooms]

Changes

Support anonymous object version definition in the sbt plugin.

Context

The following is a commonly used pattern:

val versions = new {
  example = "0.0.8"
}
libraryDependencies += "org.example" % "foo" % versions.example

This PR brings support to this, only on one level of nesting.

Please select one of the following:

• This closes an existing Issue, Closes: #
• This doesn't close an Issue, but I accept the risk that this PR may be closed if maintainers disagree with its opening or implementation

AI assistance disclosure

Did you use AI tools to create any part of this pull request?

Please select one option and, if yes, briefly describe how AI was used (e.g., code, tests, docs) and which tool(s) you used.

• No — I did not use AI for this contribution.
• Yes — minimal assistance (e.g., IDE autocomplete, small code completions, grammar fixes).
• Yes — substantive assistance (AI-generated non‑trivial portions of code, tests, or documentation).
• Yes — other (please describe):

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests, but ran on a real repository, or
• Both unit tests + ran on a real repository

The public repository: https://github.com/Thooms/renovate-example-scala-repository

Example of a created PR: Thooms/renovate-example-scala-repository#4

[cla-assistant]

All committers have signed the CLA.

[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[Thooms]

Hey @viceice 👋 I'd like to kindly ask for a review here!

[github-actions]

Hi there,

This is intended as a polite, automated request that users avoid @ mentioning repository maintainers like @viceice. Doing so causes annoying mobile notifications and makes it harder to maintain this repository.

We know it might be common elsewhere but we participate in hundreds of discussions a week and would need to turn off GitHub mobile notifications if we were mentioned in every one.

As a general rule, we will read and respond to all discussions in this repository, so there is no need to mention us.

Thanks, the Renovate team

[viceice]

• Feature freeze for Renovate 42 #40717
  ☝️

[Thooms]

Got it. Apologies for the wild ping! Won't happen again.