fix: batch consolidation for large entry counts

[BYK]

Summary

Follow-up to #473. Onur's logs revealed 1143 knowledge entries — far beyond what the single-pass consolidation can handle. The previous consolidation sent all entries in one prompt, but with 1143 entries (~343K tokens of input) this overflows the context window, and the 4096 output token budget can only express ~80-100 delete ops (vs the ~1118 needed).

Context from Onur's logs

entry count 1143 exceeds maxEntries 25 — running consolidation
entry count 1143 exceeds maxEntries 25 — running consolidation
entry count 1143 exceeds maxEntries 25 — running consolidation
...repeating every ~60s...

cost-tracker: worker overhead=$1140.8017 (distillation-only=$2.5246)

The retry storm (#473) burned $1,138 in consolidation calls that could never succeed due to the token budget constraint.

Changes

Adds batched consolidation mode in curator.ts:

• When entries ≤ 50: unchanged — sends all entries in a single prompt
• When entries > 50 (batched mode): takes the lowest-confidence entries (tail of the confidence-sorted list from forProject()) as candidates for deletion. Each pass targets removing ~25 entries (half the batch).
• The idle scheduler's cooldown (from fix: consolidation retry storm, idle curation frequency, and session memory leak #473) clears when entry count changes, automatically triggering the next batch on the following idle tick.
• Converges to maxEntries over multiple passes: 1143 → 1118 → 1093 → ... → 25

For Onur's case: ~45 passes × 1 Sonnet call each ≈ $2-3 total to clean up 1143 entries, spread across idle periods. vs the previous behavior of infinite retries that never made progress.