Fix Windows worktree create path matching

[Jinwoo-H]

Summary

• normalize worktree path comparisons so Windows worktree creation does not fail when Git reports the same path with different separators or drive-letter casing
• use the same path-equivalence helper in both the IPC create flow and the runtime-managed create flow
• add regression tests for Windows path matching and make one existing path-resolution test platform-neutral

Testing

• pnpm vitest run src/main/ipc/worktree-logic.test.ts src/main/ipc/worktrees.test.ts src/main/runtime/orca-runtime.test.ts
• pnpm tsc --noEmit -p tsconfig.node.json --composite false

Notes

• pnpm install populated dependencies, but the repo postinstall still fails on this machine when rebuilding node-pty for Electron because Visual Studio Spectre-mitigated C++ libraries are missing (MSB8040). The focused unit tests and node typecheck above passed.