fix: normalize Windows workspace namespace paths

[Reekin]

Summary

• normalize Windows \\?\ workspace paths across workspace creation, storage, and worktree flows
• keep namespace-path migrations best-effort on read so startup does not require config files to be writable
• normalize workspace/global worktree root settings and add Windows path regression coverage, including UNC dedupe

Testing

• rustfmt --edition 2021 src-tauri/src/storage.rs src-tauri/src/shared/settings_core.rs src-tauri/src/shared/workspaces_core/crud_persistence.rs src-tauri/src/shared/workspaces_core/helpers.rs src-tauri/src/shared/workspaces_core/worktree.rs src-tauri/src/workspaces/tests.rs
• git diff --check
• npm run test -- src/features/workspaces/hooks/useWorkspaces.test.tsx (blocked: vitest not installed in current environment)
• npm run typecheck (blocked: tsc not installed in current environment)
• cargo test --manifest-path src-tauri/Cargo.toml ... (blocked by existing third-party whisper-rs 0.12.0 compile errors in this environment)

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Stop retrying path migration on every workspace read

When read_workspaces sees a namespace path, it now rewrites the file on every read. In daemon mode, list_workspaces calls sync_workspaces_from_storage each request, which calls read_workspaces; if workspaces.json is read-only, changed stays true and this branch will keep attempting (and logging) a failed write on every refresh. That creates persistent stderr noise and avoidable I/O in the exact scenario this change aims to tolerate (best-effort migration when files are not writable).

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