[Feature] Add project rename and delete actions to the sidebar

[Astro-Han]

Context

Slice 09 sidebar polish is closing. Project-level lifecycle actions, rename and delete a project rather than a session, were scoped out so they do not pile onto an already-large PR.

What's missing today

The sidebar can show sessions grouped by project when sort mode is by project, but there is no UI affordance to:

• Rename a project when the project header label diverges from the directory name.
• Delete a project from the sidebar or workspace registry.

Priority triage

P2.

This is useful project-management completion work for the sidebar, but it is not a current first-run blocker or session-recovery issue. It should land after the grouped-project infrastructure is settled and should not displace P1 work on install/open, session blockers, permissions, or command-palette navigation.

Scope for this issue

• Right-click on the project header, or use an overflow button, to reveal a context menu with Rename and Delete.
• Rename: inline edit of the header label, persisted in workspace metadata. Sessions inside keep their directory.
• Delete: confirmation dialog. Choose either "remove from sidebar only" or "remove and archive sessions" and document the choice in the PR.
• i18n strings in zh and en for menu entries, dialog copy, and toast confirmations.

Out of scope

• Workspace export, project import, multi-select, drag-to-reorder.
• Anything that touches session contents. Renaming a project must not change how individual sessions are filed on disk.

Files likely touched

• packages/app/src/pages/layout/pawwork-sidebar.tsx - project header context menu and rename inline editor.
• packages/app/src/pages/layout/pawwork-session-nav.ts - group label versus directory name decoupling.
• packages/app/src/store/* - workspace registry or persisted metadata.
• packages/app/src/components/dialog-confirm-*.tsx - delete confirm dialog, or a new focused dialog.
• packages/app/src/i18n/{en,zh}.ts.

Dependencies

Land after #495 merges so the project-group infrastructure is settled.

Verification

• Add or update E2E coverage for rename and delete from the visible sidebar project group.
• Verify sessions remain associated with their original directories after rename.
• Verify delete confirmation text and cancellation behavior.
• Manually verify the changed path in Electron via bun run dev:desktop.

[Astro-Han]

Update: PR #517 implements rename + soft-hide (remove from sidebar) for projects.

Product decision: Archive sessions is intentionally out of scope. The archive feature was previously removed from the UI in commit fd14427 because it lacks a user-facing restore/unarchive path. Instead, this PR provides:

• Remove from sidebar: Soft-hide projects with Undo support and auto-restore on re-open
• Rename project: Non-destructive display name change via ProjectMeta

This covers the user-facing need of removing a project from view while keeping sessions accessible. If batch archive is needed in the future, it should come after designing an unarchive/restore UI.