Fix warpui_core StoredView compile error and tui test file naming

[warp-dev-github-integration]

Description

Fixes the two CI failures on PR #12634 (zb/tui-backend/03b-tui-elements).

1. Run Linux tests — warpui_core failed to compile

AppContext::collect_transferable_subtree calls view.child_view_ids(self) on a &StoredView (crates/warpui_core/src/core/app.rs:3306), but the StoredView enum never had a child_view_ids forwarding method, producing:

error[E0599]: no method named `child_view_ids` found for reference `&core::window::StoredView` in the current scope

This adds StoredView::child_view_ids, delegating to the GUI view (AnyView::child_view_ids) and returning an empty vec for TUI views, matching the existing neutral-hook delegation pattern in window.rs.

Note: the failing call is in app.rs and is not gated behind the tui feature, so this breaks the default build as well. The same omission exists on master (the child_view_ids call and the StoredView enum are identical there), so this also fixes a latent breakage on master caused by a semantic merge.

2. Miscellaneous checks — incorrectly named test file

CI flags any *_test.rs file (must be *_tests.rs). Renamed elements/tui/mod_test.rs → mod_tests.rs and wired it into elements/tui/mod.rs with the standard include, matching sibling test files:

#[cfg(test)]
#[path = "mod_tests.rs"]
mod tests;

Validation

• cargo check -p warpui_core (default features) — compiles
• cargo check -p warpui_core --features tui — compiles
• cargo test -p warpui_core --lib --no-run (default features, as CI builds) — compiles
• cargo fmt --check -p warpui_core — clean
• cargo clippy -p warpui_core --all-targets --tests -- -D warnings — clean
• test-file naming check and script/check_no_inline_test_modules — pass

Conversation: https://staging.warp.dev/conversation/62baaa87-02be-47dc-8ded-5130a8019d66
Run: https://oz.staging.warp.dev/runs/019ee255-0043-755f-922d-17629603cf1d

This PR was generated with Oz.