Replace static "first 3 + last 2" preservation with intelligent anchor
selection that adapts to data patterns and array size.
Key changes:
- Add AnchorSelector class for dynamic position-based preservation
- Add AnchorConfig for configurable anchor allocation (budget ratio,
strategy weights, information density scoring)
- Add content-based deduplication to prevent wasting slots on identical
items using SHA256 hashing
- Add _fill_remaining_slots() to maximize output when dedup reduces items
- Support data pattern detection (TIME_SERIES, SEARCH_RESULTS, LOGS, GENERIC)
- Support query-aware anchor adjustment for back-heavy patterns
Enterprise hardening:
- Thread-safe: No shared state modified
- O(n) performance for dedup and slot filling
- Fault-tolerant serialization with fallbacks
- Configurable via dedup_identical_items flag
52 tests covering adversarial positions, size adaptation, pattern-aware
anchoring, query-aware selection, information density, coverage metrics,
edge cases, and preservation guarantees.
