fix: listener handler_expression should generate tmp variable declarations in handler scope

[Brooooooklyn]

handler_expression was being processed without the IN_CHILD_OPERATION flag, causing temporary variables to be scoped to the parent create block instead of the listener function. This meant let tmp_N_0; declarations were missing inside listener functions that use safe navigation on function call receivers (e.g., getPopover()?.close()).

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Note

Medium Risk
Touches the compiler’s IR traversal and temporary-variable generation for event listeners, which can change emitted code and temp var naming in templates with safe navigation. Scope is narrow but could affect listener output across templates.

Overview
Fixes listener compilation so CreateOp::Listener.handler_expression is treated as part of the handler (child operation) scope during expression traversal, aligning visitor/transform flags with handler_ops.

Updates the temporary_variables phase to generate temp-variable names/declarations for handler_expression together with handler_ops (with the correct op index ordering), ensuring safe-navigation on call receivers inside listeners emits let tmp_N_0; inside the listener function.

Adds integration tests + snapshots covering safe calls/property reads in listeners, including the embedded-view (@if) case to validate correct temp naming (tmp_2_0).

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