Normalize realpath results for Windows drive roots so D:\ does not round-trip to drive-relative D: and resolve back into the current repository.
Also tighten Sidebar hidden-project matching so a drive root does not match every child project on the same drive.
Tested: bun test src/server/__tests__/windows-drive-path.test.ts src/server/__tests__/sessions.test.ts src/server/__tests__/workspace-service.test.ts
Tested: cd desktop && bun run test -- --run src/components/layout/Sidebar.test.tsx
Tested: cd desktop && bun run build:windows-x64
Tested: bun run check:desktop
Not-tested: bun run check:server (failed on existing/environment failures including the pre-existing untracked FileReadTool test)
Confidence: high
Scope-risk: narrow
Windows folder selection can surface drive roots as D:, which Node treats as drive-relative instead of the absolute D:\ root. Normalize drive-root inputs before resolving launch directories, filesystem access roots, transcript metadata, and workspace paths. Use path.relative containment checks so drive roots and child projects remain distinct in session grouping and file access.
Constraint: Windows drive-root inputs may arrive as C:, D:, or any other single-letter drive prefix
Rejected: Special-case only D: | every Windows drive letter has the same drive-relative semantics
Confidence: high
Scope-risk: moderate
Directive: Keep Windows drive-root normalization centralized; do not reintroduce string-prefix containment checks for workspace roots
Tested: bun test src/server/__tests__/windows-drive-path.test.ts src/server/__tests__/filesystem.test.ts src/server/__tests__/sessions.test.ts src/server/__tests__/workspace-service.test.ts
Tested: cd desktop && bun run test -- --run src/components/layout/Sidebar.test.tsx
Tested: bun run check:server
Tested: cd desktop && bun run lint
Not-tested: Real Windows desktop smoke on a physical Windows machine
Related: #601
