Add Highlight struct with SHA-256 hashing and improve query

- Add Highlight struct to represent bookmarks with owned memory
- Implement SHA-256 hashing for text and book identification
- Update SQL query to extract clean book filenames (removes path and fragment)
- Remove unused Annotation column from query
- Add CLAUDE.md for repository documentation
- Update .gitignore to exclude SQLite WAL files

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,82 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+A statically-linked Zig binary that extracts highlights from Kobo e-reader SQLite databases. The project builds for both x86_64 (development) and ARM (target Kobo device).
+
+## Build Commands
+
+### Local development (x86_64)
+```bash
+zig build
+./zig-out/bin/kb_exfiltrator local-dev.sqlite
+```
+
+### Run with arguments
+```bash
+zig build run -- path/to/database.sqlite
+```
+
+### Testing
+```bash
+zig build test
+```
+
+### For Kobo (ARM target)
+```bash
+./build-kobo.sh
+# or manually:
+zig build -Dtarget=arm-linux-musleabihf -Doptimize=ReleaseSmall
+```
+
+The ARM build creates `kb_exfiltrator-kobo-arm` in the project root.
+
+## Architecture
+
+### Module Structure
+
+The project uses Zig's module system with two distinct modules:
+
+- **kb_exfiltrator module** (`src/root.zig`): Library module exposing reusable functionality
+- **Executable module** (`src/main.zig`): CLI entry point that imports the library module
+
+The executable depends on the library module via the imports mechanism in build.zig:87-91.
+
+### SQLite Integration
+
+SQLite is vendored as an amalgamation build (vendor/sqlite-amalgamation-3480000/). The build.zig configuration:
+- Links SQLite as a C source file (build.zig:87-93)
+- Compiles with `SQLITE_THREADSAFE=0` (no threading, smaller binary)
+- Compiles with `SQLITE_OMIT_LOAD_EXTENSION` (security)
+- Uses `@cImport` in main.zig:2-4 to import C headers
+
+### Static Linking
+
+The binary is fully statically linked:
+- Uses musl libc for ARM target (`arm-linux-musleabihf`)
+- SQLite compiled directly into the binary
+- No external dependencies required on target device
+
+### Database Schema
+
+The program queries the Kobo `Bookmark` table:
+- `Text`: The highlighted text (non-NULL indicates a highlight)
+- `Annotation`: User's notes on the highlight (nullable)
+- `DateCreated`: Timestamp
+- `ContentID`: Book identifier
+
+Query implementation: src/main.zig:33-42
+
+### Build System Details
+
+The build.zig uses Zig's build graph system:
+- Target and optimization are configurable via CLI (`-Dtarget`, `-Doptimize`)
+- The executable step (build.zig:60-84) creates the root module and wires dependencies
+- Tests are split into module tests and executable tests (build.zig:132-154)
+- Both test suites run in parallel when executing `zig build test`
+
+## Requirements
+
+- Zig 0.15.2 or later (specified in build.zig.zon:28)