docs: add 0.1.0 upgrade guide outline

[drew]

Summary

Add a concise, audience-based outline for the OpenShell 0.1.0 upgrade guide. The page separates operator actions from end-user changes and stays intentionally brief while the remaining 0.1.0 work lands.

Related Issue

Related to #3063. This draft establishes the guide structure and breaking-change inventory; the remaining definition of done stays open for final release validation and expansion.

Changes

• Add the 0.1.0 guide with separate operator and end-user sections.
• Summarize the reviewed breaking changes with focused migration examples and links to canonical references.
• Link every migration item to its defining PR and identify contracts that are still open.
• Cover authenticated compute-driver runtime identity binding from fix(kubernetes): bind bootstrap to runtime identity #3531.
• Update workload-image and interactive-exec guidance to match the contracts landed in refactor(runtime): retire Community image dependencies #3386 and fix(exec): preserve output after stdin EOF and verify stream completion #3359.
• Add a top-level Upgrade section to the docs navigation.
• Mark the guide as a working outline while targeted changes remain in flight.

Testing

• mise run pre-commit passes
• mise run docs passes
• Unit tests added/updated (not applicable; docs-only change)
• E2E tests added/updated (not applicable; docs-only change)

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (not applicable; docs-only change)

[copy-pr-bot]

Auto-sync is disabled for draft pull requests in this repository. Workflows must be run manually.

Contributors can view more details about this message here.

[github-actions]

🌿 Preview your docs: https://nvidia-preview-pr-3540.docs.buildwithfern.com/openshell