feat: initial MCP server for printing markdown to Epson TM-m30

Single tool `print(markdown, title?, timestamp?, qr_urls?, cut?)`. Hand-rolled
line-by-line markdown parser translates headings/bold/code/lists/blockquotes/
HR/links to ESC/POS, then sends raw bytes via TCP to 192.168.0.184:9100.

Mirrors mcp-gemma4 layout (stdio server, single server.py, mcp package).

test_server.py

@@ -0,0 +1,91 @@
+"""Self-test for mcp-pos-print.
+
+Runs the same code path as the MCP `print` tool (build_receipt + send_bytes)
+without spinning up an MCP server. Prints one self-documenting page covering
+every supported markdown feature plus a QR code.
+
+Usage: .venv/bin/python test_server.py
+"""
+
+import sys
+
+from server import build_receipt, send_bytes, PRINTER_IP, PRINTER_PORT
+
+
+SELF_TEST_MD = """\
+# mcp-pos-print
+
+## Self test
+
+This page exercises every supported markdown feature. If anything here looks
+broken on the printout, the parser has a bug.
+
+### Inline formatting
+
+Plain text. **Bold text**. `inline code`. A [link to example](https://example.com)
+that gets rendered as text + url in parens. Mixed: this **bold spans `inline
+code` and continues** after the code.
+
+### Lists
+
+- First bullet, short.
+- Second bullet that runs long enough to wrap onto a continuation line so we
+  can verify the hanging indent works as expected at 57 columns.
+- Third bullet with **bold** and `code`.
+
+1. Numbered one.
+2. Numbered two with a longer body that exercises hanging-indent for the
+   numbered variant which has a different prefix width.
+3. Numbered three.
+
+### Blockquote
+
+> Single-line quote.
+
+> Long quote that needs to wrap. The pipe prefix should appear on the first
+> line; continuation lines indent under the text, not under the pipe.
+
+### Horizontal rule
+
+---
+
+### Code block
+
+```
+def hello(name):
+    print(f"hi, {name}")
+    return 42
+```
+
+### Long line
+
+This is a single very long paragraph line that should soft-wrap at the 57
+column boundary determined by Font B on 80mm thermal paper, demonstrating
+that the wrap algorithm prefers word boundaries over hard breaks.
+
+### End
+
+If all of the above rendered correctly you are good to go.
+"""
+
+
+def main() -> int:
+    raw = build_receipt(
+        markdown=SELF_TEST_MD,
+        title="mcp-pos-print",
+        timestamp=True,
+        qr_urls=["https://git.sethpc.xyz/Seth/mcp-pos-print"],
+        cut=True,
+    )
+    print(f"Built {len(raw)} bytes. Sending to {PRINTER_IP}:{PRINTER_PORT}...")
+    try:
+        send_bytes(raw)
+    except Exception as e:
+        print(f"FAIL: {type(e).__name__}: {e}", file=sys.stderr)
+        return 1
+    print("OK — check the printer.")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())