Adds a "GA source directory" setting so the packaged desktop app can run
against a standalone GenericAgent checkout instead of its own bundled
runtime/app — memory, sessions, model_responses and the agent code all
come from that 本体, live-shared with other frontends.
- lib.rs: ga_source_override settings key honored in get_or_discover_config
BEFORE the bundle default; validated (agentmain.py + desktop_bridge.py),
invalid/missing override falls back to the bundle (本体-moved safety net)
- set_ga_source / clear_ga_source / get_ga_source commands: write setting,
stop current bridge, respawn from resolved config, reload webview
- startup uses the override-aware config for takeover + spawn
- ACL grants for the three new commands
- Settings > Features UI: pick source dir, show current, clear; zh/en i18n
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
