Cherry-picked from PR #2576 by ereid7, plus read-side fix from 173a5c62.
Both fixes were originally landed in 173a5c62 but were inadvertently
reverted by commit 34be3f8b (a squash-merge that bundled unrelated
tools_config.py changes).
Save side (_save_platform_tools): exclude platform default toolset
names (hermes-cli, hermes-telegram) from preserved entries so they
don't silently re-enable everything.
Read side (_get_platform_tools): when the saved list contains explicit
configurable keys, use direct membership instead of subset inference.
The subset approach is broken when composite toolsets like hermes-cli
resolve to ALL tools.
868b3c07e3