docs: add dedicated docs website

docs/cli/index.md

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+# Command Line Interface
+
+The `@toon-format/cli` package provides a command-line interface for encoding JSON to TOON and decoding TOON back to JSON. Use it for quick conversions without writing code, estimating token savings before sending data to LLMs, or integrating TOON into shell pipelines with tools like curl and jq. It supports stdin/stdout workflows, multiple delimiter options, token statistics, and all encoding/decoding features available in the library.
+
+The CLI is built on top of the `@toon-format/toon` TypeScript implementation and adheres to the [latest specification](/reference/spec).
+
+## Usage
+
+### Without Installation
+
+Use `npx` to run the CLI without installing:
+
+::: code-group
+
+```bash [Encode]
+npx @toon-format/cli input.json -o output.toon
+```
+
+```bash [Decode]
+npx @toon-format/cli data.toon -o output.json
+```
+
+```bash [Stdin]
+echo '{"name": "Ada"}' | npx @toon-format/cli
+```
+
+:::
+
+### Global Installation
+
+Or install globally for repeated use:
+
+::: code-group
+
+```bash [npm]
+npm install -g @toon-format/cli
+```
+
+```bash [pnpm]
+pnpm add -g @toon-format/cli
+```
+
+```bash [yarn]
+yarn global add @toon-format/cli
+```
+
+:::
+
+After global installation, use the `toon` command:
+
+```bash
+toon input.json -o output.toon
+```
+
+## Basic Usage
+
+### Auto-Detection
+
+The CLI automatically detects the operation based on file extension:
+- `.json` files → encode (JSON to TOON)
+- `.toon` files → decode (TOON to JSON)
+
+When reading from stdin, use `--encode` or `--decode` flags to specify the operation (defaults to encode).
+
+::: code-group
+
+```bash [Encode JSON to TOON]
+toon input.json -o output.toon
+```
+
+```bash [Decode TOON to JSON]
+toon data.toon -o output.json
+```
+
+```bash [Output to stdout]
+toon input.json
+```
+
+```bash [Pipe from stdin]
+cat data.json | toon
+echo '{"name": "Ada"}' | toon
+```
+
+```bash [Decode from stdin]
+cat data.toon | toon --decode
+```
+
+:::
+
+### Standard Input
+
+Omit the input argument or use `-` to read from stdin. This enables piping data directly from other commands:
+
+```bash
+# No argument needed
+cat data.json | toon
+
+# Explicit stdin with hyphen (equivalent)
+cat data.json | toon -
+
+# Decode from stdin
+cat data.toon | toon --decode
+```
+
+## Options
+
+| Option | Description |
+| ------ | ----------- |
+| `-o, --output <file>` | Output file path (prints to stdout if omitted) |
+| `-e, --encode` | Force encode mode (overrides auto-detection) |
+| `-d, --decode` | Force decode mode (overrides auto-detection) |
+| `--delimiter <char>` | Array delimiter: `,` (comma), `\t` (tab), `\|` (pipe) |
+| `--indent <number>` | Indentation size (default: `2`) |
+| `--stats` | Show token count estimates and savings (encode only) |
+| `--no-strict` | Disable strict validation when decoding |
+| `--key-folding <mode>` | Key folding mode: `off`, `safe` (default: `off`) |
+| `--flatten-depth <number>` | Maximum segments to fold (default: `Infinity`) – requires `--key-folding safe` |
+| `--expand-paths <mode>` | Path expansion mode: `off`, `safe` (default: `off`) |
+
+## Advanced Examples
+
+### Token Statistics
+
+Show token savings when encoding:
+
+```bash
+toon data.json --stats -o output.toon
+```
+
+This helps you estimate token cost savings before sending data to LLMs.
+
+### Alternative Delimiters
+
+TOON supports three delimiters: comma (default), tab, and pipe. Alternative delimiters can provide additional token savings in specific contexts.
+
+::: code-group
+
+```bash [Tab-separated]
+toon data.json --delimiter "\t" -o output.toon
+```
+
+```bash [Pipe-separated]
+toon data.json --delimiter "|" -o output.toon
+```
+
+:::
+
+**Tab delimiter example:**
+
+::: code-group
+
+```yaml [Tab]
+items[2	]{id	name	qty	price}:
+  A1	Widget	2	9.99
+  B2	Gadget	1	14.5
+```
+
+```yaml [Comma (default)]
+items[2]{id,name,qty,price}:
+  A1,Widget,2,9.99
+  B2,Gadget,1,14.5
+```
+
+:::
+
+> [!TIP]
+> Tab delimiters often tokenize more efficiently than commas and reduce the need for quote-escaping. Use `--delimiter "\t"` for maximum token savings on large tabular data.
+
+### Lenient Decoding
+
+Skip validation for faster processing:
+
+```bash
+toon data.toon --no-strict -o output.json
+```
+
+Lenient mode (`--no-strict`) disables strict validation checks like array count matching, indentation multiples, and delimiter consistency. Use this when you trust the input and want faster decoding.
+
+### Stdin Workflows
+
+The CLI integrates seamlessly with Unix pipes and other command-line tools:
+
+```bash
+# Convert API response to TOON
+curl https://api.example.com/data | toon --stats
+
+# Process large dataset
+cat large-dataset.json | toon --delimiter "\t" > output.toon
+
+# Chain with jq
+jq '.results' data.json | toon > filtered.toon
+```
+
+### Key Folding
+
+Collapse nested wrapper chains to reduce tokens (since spec v1.5):
+
+::: code-group
+
+```bash [Basic key folding]
+toon input.json --key-folding safe -o output.toon
+```
+
+```bash [Limit folding depth]
+toon input.json --key-folding safe --flatten-depth 2 -o output.toon
+```
+
+:::
+
+**Example:**
+
+For data like:
+
+```json
+{
+  "data": {
+    "metadata": {
+      "items": ["a", "b"]
+    }
+  }
+}
+```
+
+With `--key-folding safe`, output becomes:
+
+```yaml
+data.metadata.items[2]: a,b
+```
+
+Instead of:
+
+```yaml
+data:
+  metadata:
+    items[2]: a,b
+```
+
+### Path Expansion
+
+Reconstruct nested structure from folded keys when decoding:
+
+```bash
+toon data.toon --expand-paths safe -o output.json
+```
+
+This pairs with `--key-folding safe` for lossless round-trips.
+
+### Round-Trip Workflow
+
+```bash
+# Encode with folding
+toon input.json --key-folding safe -o compressed.toon
+
+# Decode with expansion (restores original structure)
+toon compressed.toon --expand-paths safe -o output.json
+
+# Verify round-trip
+diff input.json output.json
+```
+
+### Combined Options
+
+Combine multiple options for maximum efficiency:
+
+```bash
+# Key folding + tab delimiter + stats
+toon data.json --key-folding safe --delimiter "\t" --stats -o output.toon
+```