refactor: rewrite in rust

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Build & Test Commands
+
+```bash
+nix develop              # Enter dev shell with Rust toolchain
+nix build                # Build the package
+nix flake check          # Run all checks (clippy, fmt, tests, pre-commit)
+
+# Inside nix develop:
+cargo test               # Run all tests
+cargo test test_name     # Run a specific test
+cargo clippy             # Lint
+cargo fmt                # Format
+```
+
+## Architecture
+
+Streamd parses markdown files into hierarchical **Shards**, then **localizes** them by assigning temporal moments and dimensional placements based on `@Tag` markers.
+
+**Data flow:** Markdown → `extract::parser` → `Shard` tree → `localize::shard` → `LocalizedShard` tree
+
+**Key modules:**
+- `models/` — Core types: `Shard`, `LocalizedShard`, `Dimension`, `Marker`, `Timecard`
+- `extract/` — Tag extraction (`tag_extraction.rs`) and markdown parsing (`parser.rs`)
+- `localize/` — DateTime extraction, configuration merging, shard localization
+- `timesheet/` — State machine that converts localized shards into timecards
+- `query/` — Recursive search functions for finding shards by predicate
+- `cli/` — Clap-based CLI commands
+
+## Requirements
+
+`REQUIREMENTS.md` contains the formal specification. Update it along with the `README.md` whenever implementing or changing features.