feat: primary workspace switch with ^ alias

[eersnington]

• Add ^ as a navi switch target for the repo-primary workspace.
• Resolve the primary workspace through validated repo-root discovery instead of assuming workspace name default.
• Update CLI help, docs, and integration coverage for primary-workspace switching.

[cubic-dev-ai]

1 issue found across 8 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="src/repo/paths.rs">

<violation number="1" location="src/repo/paths.rs:279">
P2: Don't derive the primary workspace root from `repo_storage_path` alone; absolute repo-storage pointers will make this point at the wrong directory and break `switch ^` in those repos.</violation>
</file>

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