fix(app): route to opened workspace session context

[natewill]

Summary

• prefer the opened workspace directory when resolving project navigation targets
• restore/use recent sessions scoped to that workspace before falling back to root
• navigate to the opened workspace new-session route when no workspace sessions exist

Why

After opening a sandbox/worktree, navigation could still land on the primary workspace session list instead of the opened workspace context.

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[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on my search, I found one potentially related PR:

Related PR:

• fix(session): scope session list and TUI to current directory #14489 - fix(session): scope session list and TUI to current directory
  • fix(session): scope session list and TUI to current directory #14489
  • This PR appears to address a similar concern about scoping sessions to the current/opened workspace directory, which aligns with the goal of PR fix(app): route to opened workspace session context #16549 to prefer the opened workspace directory when resolving navigation targets.

The other result (#15765) is less directly related as it focuses on an active-session endpoint rather than workspace navigation.