Respect CODEX_HOME for local storage

[cquxl]

Summary

• Resolve the default Codex local database from CODEX_HOME when it is set
• Keep the existing ~/.codex/state_5.sqlite fallback when CODEX_HOME is not configured
• Add a CLI parser test for CODEX_HOME based profile storage

Why

Tools such as CodexSwitcher launch Codex with an isolated CODEX_HOME per account. Codex++ previously always used the default user ~/.codex/state_5.sqlite path, so sidebar delete actions could fail with "Thread not found in local storage" even though the thread existed in the active profile database.

Test

• python -m pytest tests/test_launcher_cli.py::test_cli_default_db_path_uses_codex_home tests/test_launcher_cli.py::test_cli_launch_subcommand_keeps_helper_server_alive_after_injection -q

[cquxl]

Updated with an additional fix for merged/projected sidebar rows: when the helper reports "Thread not found in local storage", the renderer now removes the stale projected thread id and workspace hint before removing the row from the sidebar. This handles orphaned rows left by history/profile merging without treating unrelated delete failures as success.