`append_history` previously used `strip_think(entry) or entry.rstrip()`
as a safety net, so if the entire entry was a template-token leak (e.g.
`<think>reasoning</think>` or `<channel|>` alone), the raw leaked text
was still persisted to history — later re-introducing the very content
`strip_think` was meant to scrub, via consolidation / replay.
Persist the cleaned content directly. When cleanup empties a non-empty
entry, log at debug and store an empty-content record (cursor continuity
preserved). Adds 3 regression tests in test_memory_store.py covering:
- Well-formed thinking blocks are stripped before persistence.
- Pure-leak entries persist as empty, not as raw text.
- Malformed prefix leaks (`<channel|>`) also persist as empty.
hlgandXubin Ren
899a9073ce