fix(sidebar): persist collapsed projects

[JairEsk]

Summary

• persist collapsed sidebar project paths in local storage
• restore the collapsed state when the sidebar mounts
• safely ignore malformed stored values

Verification

• npx prettier --check src/renderer/src/components/Sidebar.tsx
• npm run typecheck:web
• npm run smoke:store
• npm run smoke:app reached and passed the project-order persistence coverage, but the full suite has one unrelated environment failure: a session without a port does not set PORT because PORT=3118 is inherited by the test process

[JairEsk]

Addressed all review items in e8a2f99:

• prune collapsed project paths against the live project list before persisting
• persist expanded subagent groups as the equivalent nested tree state, pruning deleted parent sessions
• guard both structured localStorage reads and writes
• use lowercase, versioned keys: roxy.sidebar.projects.v1 and roxy.sidebar.subagents.v1
• rename the existing rail key constant to RAIL_COLLAPSED_KEY to remove the internal ambiguity without changing its persisted key

Verification:

• npm run typecheck (node + web)
• npm run smoke:store
• npm run smoke:shared (1094 checks)
• npm run smoke:i18n (18 checks)
• npm run i18n
• npm run smoke:app with inherited PORT removed (731 checks)
• Prettier and git diff --check

All checks pass.

[JairEsk]

Correction: the review fixes are in commit b3a5d47 (the previous comment referenced the wrong short hash).