## Why
`TurnContext::cwd` is deprecated in favor of resolving paths from the
selected turn environment cwd. A few filesystem-oriented paths were
still constructing sandbox context from the legacy cwd and then mutating
it afterward, or resolving local file paths through the deprecated
helper.
## What changed
- Make `TurnContext::file_system_sandbox_context` take the trusted cwd
explicitly.
- Pass the selected turn environment cwd directly from `apply_patch` and
`view_image` call sites.
- Restrict `spawn_agents_on_csv` to exactly one local environment and
resolve input/output CSV paths from that local environment cwd.
- Remove a redundant test setup assignment that only synchronized
deprecated `TurnContext::cwd` with a replaced config.
## Validation
- `cargo test -p codex-core view_image`
- `cargo test -p codex-core
maybe_persist_mcp_tool_approval_writes_project_config_for_project_server`
- `cargo test -p codex-core parse_csv_supports_quotes_and_commas`
- `git diff --check`