fix: update 6 test files broken by dead code removal

- test_percentage_clamp.py: remove TestContextCompressorUsagePercent class
  and test_context_compressor_clamped (tested removed get_status() method)
- test_credential_pool.py: remove test_mark_used_increments_request_count
  (tested removed mark_used()), replace active_lease_count() calls with
  direct _active_leases dict access, remove mark_used from thread test
- test_session.py: replace SessionSource.local_cli() factory calls with
  direct SessionSource construction (local_cli classmethod removed)
- test_error_classifier.py: remove test_is_transient_property (tested
  removed is_transient property on ClassifiedError)
- test_delivery.py: remove TestDeliveryRouter class (tested removed
  resolve_targets method), clean up unused imports
- test_skills_hub.py: remove test_is_hub_installed (tested removed
  is_hub_installed method on HubLockFile)

tests/gateway/test_session.py

@@ -90,7 +90,10 @@ class TestSessionSourceRoundtrip:
 
 class TestSessionSourceDescription:
     def test_local_cli(self):
-        source = SessionSource.local_cli()
+        source = SessionSource(
+            platform=Platform.LOCAL, chat_id="cli",
+            chat_name="CLI terminal", chat_type="dm",
+        )
         assert source.description == "CLI terminal"
 
     def test_dm_with_username(self):
@@ -143,7 +146,10 @@ class TestSessionSourceDescription:
 
 class TestLocalCliFactory:
     def test_local_cli_defaults(self):
-        source = SessionSource.local_cli()
+        source = SessionSource(
+            platform=Platform.LOCAL, chat_id="cli",
+            chat_name="CLI terminal", chat_type="dm",
+        )
         assert source.platform == Platform.LOCAL
         assert source.chat_id == "cli"
         assert source.chat_type == "dm"
@@ -267,7 +273,10 @@ class TestBuildSessionContextPrompt:
 
     def test_local_prompt_mentions_machine(self):
         config = GatewayConfig()
-        source = SessionSource.local_cli()
+        source = SessionSource(
+            platform=Platform.LOCAL, chat_id="cli",
+            chat_name="CLI terminal", chat_type="dm",
+        )
         ctx = build_session_context(source, config)
         prompt = build_session_context_prompt(ctx)