How an option's raw env/TOML value is coerced to a typed value.
All kinds flow through resolve_scalar. The scalar kinds (BOOL,
BOOL_PRESENCE, INT, FLOAT, STR) are coerced inline by
_coerce_env/_coerce_toml. LOG_LEVEL_DELEGATE, SHELL_LIST_DELEGATE,
SKILLS_DIRS_DELEGATE, PTC_DELEGATE, and STARTUP_MODE_DELEGATE defer to
bespoke parsers (their semantics ā dynamic debug fallback, colon-split Path
resolution, comma + recommended/all sentinels, and the PTC/startup-mode
allowlists ā do not compress into a generic coercion). THEME_DELEGATE is
resolved separately at the top of resolve_scalar and never reaches the
inline coercers. STRUCTURED marks user-defined tables that the scalar
resolver only passes through for display.
