fix(security): re-resolve checkpoint/sticker-cache paths per call

tools/checkpoint_manager.py's CHECKPOINT_BASE and gateway/sticker_cache.py's
CACHE_PATH are resolved once at import time via get_hermes_home(), which is
a context-local ContextVar under the multiplexed gateway (multiple profiles
sharing one process). Freezing the path at import time pins every later
checkpoint/cache read-write to whichever profile's HERMES_HOME was active
when the module was first imported -- the same bug class already fixed for
cache dirs, skills_hub, rich_sent_store, and (this session) the OAuth/auth.json/
sessions.json paths.

CheckpointManager is "owned by AIAgent" per-instance, but its methods read
the frozen module constant directly instead of taking the store root from
the instance, so a profile's CheckpointManager can read/write code-edit
checkpoints into a different profile's store.

Add a per-call resolver for each path, following the established "respect
an existing test monkeypatch of the constant, otherwise re-resolve through
get_hermes_home()" pattern so the extensive existing test seams in
tests/tools/test_checkpoint_manager.py and tests/gateway/test_sticker_cache.py
keep working unmodified.

(cherry picked from commit 03ae075d969094cb584e6ab38d2a773d15ff875c)
(cherry picked from commit b850c4b18e2ae2158a97c6cb87bd2057918b8170)

tests/test_profile_isolation_runtime.py

@@ -156,6 +156,47 @@ class TestGatewayHooksDirResolution:
         assert "only-in-b" in b_hooks
 
 
+class TestCheckpointManagerPathResolution:
+    """tools/checkpoint_manager.py's checkpoint store root must honor the
+    active profile — otherwise one profile's CheckpointManager instance can
+    read/write code-edit checkpoints into a different profile's store under
+    the multiplexed gateway."""
+
+    def test_checkpoint_base_follows_override(self, two_profiles):
+        prof_a, prof_b = two_profiles
+        import tools.checkpoint_manager as cm
+
+        a_seen = _under_override(prof_a, lambda: cm._resolve_checkpoint_base())
+        b_seen = _under_override(prof_b, lambda: cm._resolve_checkpoint_base())
+
+        assert a_seen == prof_a / "checkpoints"
+        assert b_seen == prof_b / "checkpoints"
+        assert a_seen != b_seen
+
+    def test_store_path_follows_override(self, two_profiles):
+        prof_a, prof_b = two_profiles
+        import tools.checkpoint_manager as cm
+
+        b_seen = _under_override(prof_b, lambda: cm._store_path())
+        assert b_seen == prof_b / "checkpoints" / "store"
+
+
+class TestStickerCachePathResolution:
+    """gateway/sticker_cache.py's cache file must honor the active profile —
+    otherwise one profile's Telegram sticker-description cache leaks into a
+    different profile's under the multiplexed gateway."""
+
+    def test_cache_path_follows_override(self, two_profiles):
+        prof_a, prof_b = two_profiles
+        import gateway.sticker_cache as sc
+
+        a_seen = _under_override(prof_a, lambda: sc._resolve_cache_path())
+        b_seen = _under_override(prof_b, lambda: sc._resolve_cache_path())
+
+        assert a_seen == prof_a / "sticker_cache.json"
+        assert b_seen == prof_b / "sticker_cache.json"
+        assert a_seen != b_seen
+
 
 # ---------------------------------------------------------------------------
 # M2 — thread / executor context propagation