cli: remove legacy profile v1 plumbing

[jif-oai]

Why

#23883 moved the user-facing --profile flag onto profile v2. The shared CLI option layer still carried the old config_profile slot and several CLI entrypoints still copied that value into legacy config overrides. Leaving that path around makes the CLI surface look like it still selects legacy [profiles.*] state even though --profile now means $CODEX_HOME/<name>.config.toml.

What

• Remove the legacy config_profile field and merge/copy path from SharedCliOptions.
• Stop forwarding profile-v1 overrides from CLI, exec, TUI, doctor, debug, feature, and exec-server paths; runtime profile selection remains on config_profile_v2 through loader_overrides_for_profile.
• Resolve local OSS provider selection from the base config in exec and TUI now that the legacy profile argument is gone.

Testing

• Not run (cleanup-only follow-up to cli: rename profile v2 flag to --profile #23883).