fix curr_mod not refreshed on in-hook run transitions

[williballenthin]

Summary

• Refresh curr_mod from run.start_addr in _prepare_run_context so every run — whether entered via start() or _exec_next_run() — has the correct current module before any hooks fire.
• Remove the now-redundant curr_mod assignment at the top of _execute_runs's while loop, since _prepare_run_context always runs first.

Previously, curr_mod was only set inside the _execute_runs loop. In-hook run transitions via _exec_next_run → _prepare_run_context never refreshed it, so handle_import_func could consult the wrong module's import table when control transferred to a different module.

Closes #306

🤖 Generated with Claude Code

[gemini-code-assist]

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