fix(profiles): pin the launch home so a mirrored HERMES_HOME cannot flip routed-profile decisions

Symptom: a host that serves several profiles from one process and mirrors
the active turn's profile into `os.environ["HERMES_HOME"]` for legacy
readers (Hermes WebUI does this on every chat turn, next to the
context-local override) makes every launch-home decision see the served
profile as the launch profile. Two profiles that both configure `atlassian`
with different credentials share whichever MCP connection came first: a
READ_ONLY_MODE=false profile ends up calling a read-only server
(nesquena/hermes-webui#7721). The same misjudgement leaves the launch
residue in the served profile's child env, seeds the launch profile's
bridged allow-all grant into the served profile's secret scope, and lets
the served profile's `terminal.*` config bridge into the shared process env.

Cause: four launch-home checks compare the task's override with
`get_process_hermes_home()`, which reads `HERMES_HOME` live:
`agent.secret_scope.serves_routed_profile` (keys the MCP ledger via
`_mcp_registry_scope`, #108352 / #111481, and the check_fn cache, #111151),
`agent.secret_scope._is_process_home`, `tools.environments.local._is_routed_home`
and `hermes_cli.env_loader._process_hermes_home`. Under the mirror the two
sides are equal for every turn.

Change: `hermes_constants.pin_process_hermes_home(path | None)` lets the
host record the home it serves as its own; `get_routing_process_hermes_home()`
returns the pin when set, else `get_process_hermes_home()`; the four checks
compare against it. The pin is deliberately NOT folded into
`get_process_hermes_home()`: `get_hermes_home()` falls back to it for tasks
carrying no override (MCP loop, spawners), and the host's mirror exists
precisely so those readers see the served profile. Only "is this task
routed / is this the launch home" changes. Unpinned, behaviour is
byte-for-byte the old one; hosts that never mutate `HERMES_HOME` need not
call it. `activate_multi_profile_hosting()` is not the seam for this: it
flips `get_secret` fail-closed process-wide and freezes the launch env,
which an embedding host cannot adopt as a bug fix.

Tests (2 invariants, parametrized over the four checks plus the MCP ledger
key; red on main, green here): pinned + mirrored env -> the served home is
routed and the launch home is not, the MCP key is `(home_key, name)`,
`get_process_hermes_home()` still follows the env var; never pinned or
pinned-then-cleared -> old semantics, including "a mirrored env var IS the
launch home". `tests/conftest.py` resets the pin per test so the
module-global cannot leak between files.

Live repro (WebUI + a stdio FastMCP server named `atlassian` in two
profiles, one gated by READ_ONLY_MODE): base -> one ledger key
`'atlassian'`, the write profile lists only the read-only tools; fixed ->
`(<read_home_key>, 'atlassian')` and `(<write_home_key>, 'atlassian')`,
each profile lists its own tools.

Docs: `gateway/AGENTS.md` § Profile scope (one launch-home identity) and the
isolation table in `website/docs/user-guide/multi-profile-gateways.md`.
Also maps the author e-mail under contributors/emails/ (attribution check).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tools/environments/local.py

@@ -410,10 +410,14 @@ def served_profile_child_env(
 
 
 def _is_routed_home(target_home: "str | Path") -> bool:
-    """True when ``target_home`` is not the process's own (launch) home."""
-    from hermes_constants import get_process_hermes_home
+    """True when ``target_home`` is not the process's own (launch) home.
+
+    Same launch-home identity as ``agent.secret_scope.serves_routed_profile()``: under a host that
+    mirrors the served profile into ``HERMES_HOME``, the live env var names the served home and the
+    launch residue would never be stripped from that profile's child env."""
+    from hermes_constants import get_routing_process_hermes_home
     try:
-        return Path(target_home).resolve() != get_process_hermes_home().resolve()
+        return Path(target_home).resolve() != get_routing_process_hermes_home().resolve()
     except OSError:
         return True