Add `positron` to dependency version management

[bschwedler]

https://cdn.posit.co/positron/releases/pwb/arm64/all-releases.json
https://cdn.posit.co/positron/releases/pwb/x86_64/all-releases.json

These URLs will only include the last 18 months of the releases.

[bschwedler]

This was completed in:

• Add Positron as a bakery dependency #389
• Add positron init images-workbench#42

[bschwedler]

CVP/TDP Assessment

🤖 This comment was auto-generated by an AI assistant using the cvp-tdp-tagger skill. Scores reflect a judgment call based on available context at time of tagging — not an algorithmic determination.

Dimension	Score	Scale definition
CVP	cvp:0	No direct customer value — infra, tech debt, epic splits
TDP	tdp:1	The individual working on it notices

Reasoning: Enables Positron in images. Individual notices.

Context used: title+body+1 comment

Scale references: CVP · TDP