docs: expand README with project overview, concepts, and usage

README.md

@@ -1,7 +1,34 @@
 # streamer
 
-Searching for `@tags` in time-based [streams](https://www.cs.yale.edu/homes/freeman/lifestreams.html).
+Streamer is a personal knowledge management and time-tracking CLI tool. It organizes time-ordered markdown files using `@tag` annotations, letting you manage tasks, track time, and query your notes from the terminal.
 
-# Usage
+## Core Concepts
 
-Running `streamer` finds all lines with @Task
+- **Shards** — Sections of markdown files, organized hierarchically by headings. Each shard can contain markers, tags, and nested child shards.
+- **Markers** — Special `@tags` like `@Task`, `@Done`, `@Waiting`, or `@Timesheet` that give shards semantic meaning and place them into dimensions.
+- **Dimensions** — Classification axes (e.g. task state, project, timesheet) that categorize shards. Some dimensions propagate to child shards.
+
+## File Format
+
+Markdown files are named with a timestamp: `YYYYMMDD-HHMMSS [markers].md`
+
+For example: `20260131-210000 Task Streamer.md`
+
+Within files, `@`-prefixed markers at the beginning of paragraphs or headings define how a shard is categorized.
+
+## Commands
+
+- `streamer` / `streamer new` — Create a new timestamped markdown entry, opening your editor
+- `streamer todo` — Show all open tasks (shards with `@Task` markers)
+- `streamer edit [number]` — Edit a stream file by index (most recent first)
+- `streamer timesheet` — Generate time reports from `@Timesheet` markers
+
+## Configuration
+
+Streamer reads its configuration from `~/.config/streamer/config.yaml` (XDG standard). The main setting is `base_folder`, which points to the directory containing your stream files (defaults to the current working directory).
+
+## Usage
+
+Running `streamer` opens your editor to create a new entry. After saving, the file is renamed based on its timestamp and any markers found in the content.
+
+Running `streamer todo` finds all shards marked as open tasks and displays them as rich-formatted panels in your terminal.