fix: generate catalog when user configures context window (#1594)

[dongyu23]

Summary

Completes PR #1722 by fixing the two failing integration tests.

PR #1722 fixed the early return in apply_model_catalog_to_config that silently dropped the Manager's context window for suffixless custom models. Without the fix, Codex fell back to its bundled 272000 default and the CLI showed ~258K instead of the configured value (#1594).

The fix moves the fallback parse before the early return and adds fallback.is_none() to the guard, so a user-configured context window forces catalog generation.

Test fixes

Two integration tests failed because they set context_window=200000 while asserting no catalog generation. With the fix, configuring a context window now correctly triggers generation.

• apply_relay_profile_does_not_write_model_catalog_json_for_selected_models: removed context_window / auto_compact_limit, preserving the original intent — no catalog when nothing is customized.
• apply_relay_profile_no_catalog_when_model_list_has_no_suffix → renamed to apply_relay_profile_generates_catalog_when_context_window_configured: now tests the positive case — context_window set, no suffix → catalog IS generated with the correct window value in both config.toml and the catalog JSON.

Verification

cargo fmt --all -- --check   ✅
cargo clippy -p codex-plus-core --all-targets   ✅ (zero warnings on changed code)
cargo test -p codex-plus-core --test relay_config   ✅ 107 passed, 0 failed
cargo test -p codex-plus-core --lib   ✅ 209 passed, 0 failed

Closes #1722
References #1594