fix(container-use): pass source when wrapping terminal command

[cyq1017]

Fixes #334\n\n## Summary\n- Use the explicitly opened repository source path for dagger run --source in terminal auto-wrap mode, replacing the previous cwd-based lookup.\n- Update Windows terminal wrapper execution so it honors the provided arguments and now passes the generated --source argument to the wrapped command correctly.\n\n## Testing\n- go test ./cmd/container-use -run TestTerminal -count=1\n- go test -short ./...\n- git diff --check\n

[awdemos]

Endorsed for merge.

• Passes the repository source path via --source when re-execing container-use terminal through dagger run, which fixes the wrapped command's context.
• Also corrects the Windows execDaggerRun path to use the supplied args instead of rebuilding from os.Args.
• Includes focused unit tests for the new helpers.
• Verified: go test -short ./cmd/container-use/... passes.

One small suggestion: add a sentence to the PR description explaining why --source is needed for future readers. Code is good to land.