Phase 2 of #4662. reload_config() did a raw yaml.safe_load of config.yaml on
every call (~125ms+ on a large file), including on the profile-switch hot path
(~446ms load_settings stage in /api/sessions diagnostics). It now parses through
the mtime+size-keyed cache added in #4652, via a shared _load_yaml_config_file_raw
core (DRY: _load_yaml_config_file = raw + env-expand). reload_config still runs
its OWN env expansion pinned to the unscoped process-env view (block_process_env_fallback
reset + _thread_ctx.env={}) so the #798 TLS profile-isolation invariant is byte-for-byte
preserved; only the disk parse is now cached. An unchanged config.yaml is no longer
reparsed; an mtime change still busts the cache.
nesquena-hermes
8006db22fc