[GREEN] Move repository and source management into route content

[ksamaschke]

Phase

GREEN

## Deliverable
Implement the minimum content and state changes needed to move repository and source-management workflows into route content.

## Dependencies
- Parent work item: #216.

## Completion evidence
- Implementation notes covering the new source-management placement.

• Evidence that the RED tests now pass.

  Acceptance criteria

  • Repository and source operations live in route content.

• The main shell no longer relies on a Settings tab for these workflows.

  Parent: Work Item: Move repository and source management into route-based content #216

[ksamaschke]

GREEN is complete in the dedicated worktree branch codex/216-sources-route-20260315075125.

Implemented in the desktop main window:

• moved Repository Management, Source Publish Settings, and Add Repository into the Sources route content
• updated desktop-shell.ts so the Sources route explicitly owns repository/source-management workflows
• reduced the dedicated Settings window to appearance + installer defaults only

Validation so far:

• npm run build:quick
• node --test dist/tests/installer/desktop-source-route-red-phase.test.js dist/tests/installer/desktop-shell-ux.test.js dist/tests/installer/desktop-settings-window-red-phase.test.js dist/tests/installer/desktop-sidebar-routes-red-phase.test.js dist/tests/installer/dashboard-source-actions-style.test.js dist/tests/installer/source-management-state.test.js