fix(catalog): honor Manager context window for suffixless custom models (#1594)

[LeoLin990405]

Root cause

apply_model_catalog_to_config returns before generating a catalog when a custom model has neither a [window] suffix nor bundled metadata — even if the user configured a context window in the Manager. The parse_optional_positive_u64(&profile.context_window, …) that reads the user's value sat after that early return, so it never ran. Codex then falls back to its bundled 272000 default (→ 272000 − 13840 reserved ≈ 258160, the "258K" users report) regardless of the 1M they set.

Repro (from #1594): custom provider on http://127.0.0.1:57321/v1, model deepseek-v4-flash (native 1M), Manager context window = 1,000,000 → Codex CLI shows 258K / 258K for every model.

Fix

Parse the configured window first, then generate the catalog whenever there is anything to customize — a [window] suffix, bundled metadata, or a user-supplied context window. When the user set no window, behavior is unchanged (a plain custom model still gets no generated catalog).

let fallback = parse_optional_positive_u64(&profile.context_window, "上下文大小")?;
if fallback.is_none()
    && !entries.iter().any(|entry| {
        entry.suffix_window.is_some()
            || crate::model_suffix::requires_bundled_metadata_catalog(&entry.slug)
    })
{
    return Ok(config_text.to_string());
}

Verification

New regression test generates_catalog_with_user_context_window_for_suffixless_custom_model (RED before the fix, GREEN after). cargo test -p codex-plus-core --lib → 202 passed, 0 failed.

Fixes #1594.