test: strengthen assertions across 7 test files (batch 1)

Replaced weak 'is not None' / '> 0' / 'len >= 1' assertions with
concrete value checks across the most flagged test files:

gateway/test_pairing.py (11 weak → 0):
  - Code assertions verify isinstance + len == CODE_LENGTH
  - Approval results verify dict structure + specific user_id/user_name
  - Added code2 != code1 check in rate_limit_expires

test_hermes_state.py (6 weak → 0):
  - ended_at verified as float timestamp
  - Search result counts exact (== 2, not >= 1)
  - Context verified as non-empty list
  - Export verified as dict, session ID verified

test_cli_init.py (4 weak → 0):
  - max_turns asserts exact value (60)
  - model asserts string with provider/name format

gateway/test_hooks.py (2 zero-assert tests → fixed):
  - test_no_handlers_for_event: verifies no handler registered
  - test_handler_error_does_not_propagate: verifies handler count + return

gateway/test_platform_base.py (9 weak image tests → fixed):
  - extract_images tests now verify actual URL and alt_text
  - truncate_message verifies content preservation after splitting

cron/test_scheduler.py (1 weak → 0):
  - resolve_origin verifies dict equality, not just existence

cron/test_jobs.py (2 weak → 0 + 4 new tests):
  - Schedule parsing verifies ISO timestamp type
  - Cron expression verifies result is valid datetime string
  - NEW: 4 tests for update_job() (was completely untested)

tests/test_hermes_state.py

@@ -43,7 +43,7 @@ class TestSessionLifecycle:
         db.end_session("s1", end_reason="user_exit")
 
         session = db.get_session("s1")
-        assert session["ended_at"] is not None
+        assert isinstance(session["ended_at"], float)
         assert session["end_reason"] == "user_exit"
 
     def test_update_system_prompt(self, db):
@@ -138,7 +138,7 @@ class TestFTS5Search:
         db.append_message("s1", role="assistant", content="Use docker compose up.")
 
         results = db.search_messages("docker")
-        assert len(results) >= 1
+        assert len(results) == 2
         # At least one result should mention docker
         snippets = [r.get("snippet", "") for r in results]
         assert any("docker" in s.lower() or "Docker" in s for s in snippets)
@@ -174,8 +174,10 @@ class TestFTS5Search:
         db.append_message("s1", role="assistant", content="Kubernetes is an orchestrator.")
 
         results = db.search_messages("Kubernetes")
-        assert len(results) >= 1
+        assert len(results) == 2
         assert "context" in results[0]
+        assert isinstance(results[0]["context"], list)
+        assert len(results[0]["context"]) > 0
 
 
 # =========================================================================
@@ -266,7 +268,7 @@ class TestDeleteAndExport:
         db.append_message("s1", role="assistant", content="Hi")
 
         export = db.export_session("s1")
-        assert export is not None
+        assert isinstance(export, dict)
         assert export["source"] == "cli"
         assert len(export["messages"]) == 2
 
@@ -312,7 +314,9 @@ class TestPruneSessions:
         pruned = db.prune_sessions(older_than_days=90)
         assert pruned == 1
         assert db.get_session("old") is None
-        assert db.get_session("new") is not None
+        session = db.get_session("new")
+        assert session is not None
+        assert session["id"] == "new"
 
     def test_prune_skips_active_sessions(self, db):
         db.create_session(session_id="active", source="cli")