chore: code review cleanup — fixes, deps, docs

Fixed:
- CLI help typo: "metatdata" -> "metadata"
- Filter buffer OOM: check size before loading into memory

Changed:
- #[inline] on HTML escape helpers for hot path performance
- Replaced once_cell and lazy_static with std::sync::LazyLock
- Removed unused once_cell and lazy_static crate dependencies

Refactored:
- Added module-level doc to services/ module

Documentation:
- README.md: zstd is native not external, "none" -> "raw"
- DESIGN.md: current schema and meta plugins section
- CHANGELOG.md: Unreleased section populated

CHANGELOG.md

@@ -7,6 +7,30 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Database index on `items(ts)` column for faster ORDER BY sorting
+
+### Changed
+
+- Filter plugins check size before loading content into memory (prevents OOM on large inputs)
+- `#[inline]` on HTML escape helper functions (`esc`, `esc_attr`) for hot path performance
+- Removed `once_cell` crate (replaced with `std::sync::LazyLock` from Rust 1.80)
+- Removed `lazy_static` crate (replaced with `std::sync::LazyLock`)
+
+### Fixed
+
+- CLI help text typo: "metatdata" → "metadata" in `--get` and `--info` descriptions
+
+### Refactored
+
+- Added module-level documentation to `services/` module
+
+### Documentation
+
+- README.md: Fixed compression table — zstd is native (not external), "none" renamed to "raw"
+- DESIGN.md: Updated schema to reflect current `items` table columns and meta plugin inventory
+
 ## [0.1.0] - 2026-03-21
 
 ### Added