Follow-up to the /memory approve fresh-store fix. Both the CLI fallback and
the messaging-gateway handler built a bare MemoryStore() with the hardcoded
default char limits (2200/1375), ignoring the user's configured
memory.memory_char_limit / user_char_limit. A live agent honors those
overrides (agent/agent_init.py), so an approval applied without a live agent
could accept a write the user's lower cap would reject, or vice versa.
Extract a shared tools.memory_tool.load_on_disk_store() factory that reads
the configured limits (falling back to defaults if config can't load) and
wire both the CLI and gateway handlers to it, closing the gap on both
surfaces and de-duplicating the construction block.
0e69cd4b37