Add 'Move to Active' button on completed sessions

[dhilgaertner]

Closes #186

Summary

• Adds a Move to Active button to the session detail view, gated on session.status == .completed, that flips the session back to active.
• Sits alongside the existing Open in VS Code / Mark as Completed buttons and is mutually exclusive with the latter (which only shows for .active/.inReview).
• Follows the existing pattern exactly: new onSetSessionActive closure on AppState, setSessionActive(id:) helper on SessionService reusing the private updateSessionStatus(_:to:), wired in AppDelegate. No new RPC — the set-status handler and CLI already support arbitrary statuses.

Test plan

• Build with make build (passes locally)
• On an active session, click Mark as Completed → confirm it disappears and Move to Active appears in its place
• Click Move to Active → status returns to active, button disappears, Mark as Completed reappears
• Confirm the change persists across app restart
• Confirm the button is hidden on the Manager session (covered by the existing session.id != AppState.managerSessionID guard wrapping the action-button group)

🤖 Generated with Claude Code

[dgershman]

Code & Security Review

Critical Issues

None.

Security Review

Strengths:

• No new RPC surface or external input handling — reuses the existing set-status pathway
• The [weak service] capture in AppDelegate.swift:157 correctly avoids retain cycles, matching the pattern used by all adjacent closures
• No user input is taken by the button; it passes a known session.id UUID through an already-validated code path

Concerns:

• None identified

Code Quality

• Clean, minimal change that follows the existing patterns exactly (completeSession / setSessionInReview → setSessionActive)
• The SessionDetailView button visibility is correctly gated: Mark as Completed shows for .active/.inReview, Move to Active shows for .completed — mutually exclusive as described
• The Manager session guard (session.id != AppState.managerSessionID) already wraps the entire action-button group, so no additional guard is needed
• Good SF Symbol choice (arrow.uturn.backward.circle) — communicates "undo/revert" intent clearly

Summary Table

Priority	Issue
✅	No blocking issues found

Recommendation: Approve — this is a straightforward, well-scoped addition that reuses existing infrastructure (updateSessionStatus) without introducing new API surface, state, or complexity. The 22 lines added are consistent with established patterns across all four files.