Native Memory index fails closed on blank events.jsonl lines

[MohabMohie]

Problem

shaft-memory search_memory failed closed during #5207 with:

MemoryIndexUnavailable / MemoryInvalidJsonl: Blank JSONL lines are not allowed.
path: .memory/events.jsonl:1176

Line 1176 is a blank line between two otherwise valid memory.updated / memory.created events (timestamps 2026-08-18T20:21:32+03:00 and 2026-08-18T14:40:29+03:00). Retrieval and remember are unavailable until the index can load.

Not a duplicate of

• GitHub reports .memory/events.jsonl PRs as CONFLICTING despite .gitattributes merge=union #4137 — GitHub CONFLICTING on merge=union for this file
• Native Memory index fails closed on project-scoped gotcha task field #5136 — project-scoped gotcha task field (closed)

Suggested repair

• Reader: skip blank lines instead of fail-closed, or
• Writer/merge: never emit a blank line into events.jsonl

Ordinary tasks should keep treating the store as degraded until this is fixed. Do not rewrite history.

Related to #5207.