fix(memory-core): stream embedding cache seed to avoid V8 heap OOM

[lesaai]

Canary candidate. Do not npm-link to live Lēsa until canary passes.

Summary

Primary R2.A OOM fix. seedEmbeddingCache no longer materializes the full embedding_cache table with .all(); rows now stream one at a time through .iterate() inside the same BEGIN/COMMIT upsert transaction.

Repro (before this patch)

On a long-running deployed main.sqlite (observed: 16 GB, 435,136 embedding_cache rows × ~20 KB serialized text each = 8.68 GB), SELECT * FROM embedding_cache via .all() materializes the entire result set into a JS array. V8's default ~4 GB heap limit is exceeded and the gateway aborts with:

FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory
... node::sqlite::StatementSync::All ...

This reproduced locally on broad memory-heavy operations (e.g. recall/status compilation during a history review). LaunchAgent respawn keeps the service alive but it's a hard crash on every qualifying read.

Fix

1. .all() → .iterate() on the SELECT
2. Drops the if (!rows.length) return gate (iterators don't have .length); empty iterator commits a no-op transaction, which is cheap and behaviorally equivalent
3. Peak V8 heap stays bounded by a single row (~20 KB) + prepared statements instead of the whole table

Validation

• pnpm tsgo:prod: green (core + extensions graphs)
• pnpm test extensions/memory-core: 512 passed, 3 skipped, 0 failed

Scope / not in this patch

• Secondary .all() at extensions/memory-core/src/memory/manager-search.ts:246-252 (listChunks used by the keyword-fallback ranker) is a bigger surgery. Caller needs the full candidate set for accurate cosine-similarity top-K ranking, so converting to streaming requires refactoring the caller to a bounded top-K heap. Follow-up PR once this canaries clean.
• No upstream PR yet; this lives on the WIP fork only.

Canary plan

1. Canary-install this branch (not live Lēsa)
2. Repro target: Day 63-style broad memory review, or any operation triggering seedEmbeddingCache on gateway init
3. Pass criteria: no Abort trap: 6, no PID change, no V8 heap-limit FATAL, openclaw doctor clean
4. If clean, promote; then tackle the secondary listChunks path