fix(env-loader): split source_supplied_names() out of secret_source_names()

Widening secret_source_names() to include skipped_existing names silently changed
tools/mcp_tool_config.py::_build_safe_env, an untouched consumer that forwards every
returned name into MCP stdio child envs. That consumer wants only names a source
actually APPLIED (pre-stack semantics), so secret_source_names() goes back to
tuple(_SECRET_SOURCES).

The routed-child scrub in strip_launch_profile_env is the one site that must also see
names a source supplied but lost to a pre-existing process value, so it reads the new
source_supplied_names() accessor instead. tools/mcp_tool_config.py is byte-identical to
origin/main.

tools/environments/local.py

@@ -354,7 +354,7 @@ def strip_launch_profile_env(env: dict, target_home: "str | Path | None" = None)
     if Path(target).resolve() == launch_home.resolve():
         return env
     from hermes_cli.config import TERMINAL_CONFIG_ENV_MAP
-    from hermes_cli.env_loader import launch_dotenv_keys, managed_dotenv_keys, secret_source_names
+    from hermes_cli.env_loader import launch_dotenv_keys, managed_dotenv_keys, source_supplied_names
     # Current file AND every key any dotenv load put into os.environ this process lifetime: a key
     # removed or renamed in the launch .env after boot is still in os.environ with the old value, and
     # a re-parse of the file alone no longer names it (#107695 review). External secret sources
@@ -364,7 +364,7 @@ def strip_launch_profile_env(env: dict, target_home: "str | Path | None" = None)
     # .env is NOT residue: its values are policy for every profile (``_apply_managed_env`` applies
     # it last, with override, so it beats the user's own .env) — leave them in place.
     residue = set(load_env_file(launch_home / ".env")) | set(launch_dotenv_keys()) | set(TERMINAL_CONFIG_ENV_MAP.values())
-    residue |= set(secret_source_names())
+    residue |= set(source_supplied_names())
     residue -= set(managed_dotenv_keys())
     for key in residue:
         if not _is_global_env(key) or key.startswith("TERMINAL_"):