V1.0: Class 1 fax — real-world 4-page send to external number confirmed

Core features:
- Class 1 T.30 protocol: full send/receive implementation
- HDLC: DLE-stuffing, FCS strip, USR5637 bit-reversal handling
- T.4 MH encoder/decoder (1728px A4 standard)
- Document pipeline: PDF (Ghostscript), PNG, TIFF input
- Width clamping: US Letter 1734px → 1728px fax standard
- Cover page: CJK rasterization (TW/CN/JP/EN), TIFF + HTML output
- OCR verification: Tesseract 5 with eng+chi_tra, CJK space-tolerant
- API server (axum): health, send, jobs, cover, retry, cancel
- Background worker: auto-poll queue, speed fallback, retry policy
- Modem detection, pool management

Real-world test results (2026-07-23):
- V90 → 25153038: 4 pages, V.17 12000 bps, 2:33 ✅
- USR5637 → 25153038: 4 pages, V.17 12000 bps, 2:26 ✅
- Both faxes confirmed received on remote machine

Tested: loopback (100% pixel match), multi-page, all input formats,
cover pages, OCR verify, API endpoints, worker processing.
13 unit tests pass, 0 new clippy warnings.

demo/create_demo_doc.py

@@ -0,0 +1,86 @@
+#!/usr/bin/env python3
+"""Generate a demo business letter as a fax-ready TIFF."""
+from PIL import Image, ImageDraw, ImageFont
+import sys, os
+
+W, H = 1728, 2291  # A4 at 204x196 dpi
+
+def create_demo_document(output_path):
+    img = Image.new('L', (W, H), 255)
+    draw = ImageDraw.Draw(img)
+
+    # Try to load fonts — fall back to default
+    try:
+        title_font = ImageFont.truetype('/System/Library/Fonts/Helvetica.ttc', 72)
+        h1_font    = ImageFont.truetype('/System/Library/Fonts/Helvetica.ttc', 48)
+        body_font  = ImageFont.truetype('/System/Library/Fonts/Helvetica.ttc', 36)
+        small_font = ImageFont.truetype('/System/Library/Fonts/Helvetica.ttc', 28)
+    except:
+        title_font = h1_font = body_font = small_font = ImageFont.load_default()
+
+    # ── Letterhead ──
+    draw.rectangle([0, 0, W, 180], fill=0)
+    draw.text((80, 40),  "TELFAX CORPORATION", fill=255, font=title_font)
+    draw.text((80, 130), "Digital Fax Solutions", fill=200, font=small_font)
+
+    # horizontal rule
+    draw.line([80, 200, W-80, 200], fill=100, width=4)
+
+    # ── Date & Reference ──
+    draw.text((80, 240), "Date:       July 21, 2026", fill=0, font=body_font)
+    draw.text((80, 290), "Reference:  TFX-2026-07-21-001", fill=0, font=body_font)
+    draw.text((80, 340), "To:         ACME Corporation", fill=0, font=body_font)
+    draw.text((80, 390), "            Attn: Mr. John Smith", fill=0, font=body_font)
+    draw.text((80, 440), "            Fax: +1-555-0199", fill=0, font=body_font)
+    draw.text((80, 490), "From:       Jane Doe, CTO", fill=0, font=body_font)
+    draw.text((80, 540), "            Telfax Corp", fill=0, font=body_font)
+    draw.text((80, 590), "            Fax: +886-2-2748-6656", fill=0, font=body_font)
+
+    draw.line([80, 640, W-80, 640], fill=0, width=2)
+
+    # ── Subject ──
+    draw.text((80, 680), "Subject:  Business Proposal for Enterprise Fax Solution", fill=0, font=h1_font)
+
+    # ── Body ──
+    body_text = [
+        "Dear Mr. Smith,",
+        "",
+        "We are pleased to submit our proposal for an enterprise-grade digital",
+        "fax solution to replace ACME Corporation's legacy fax infrastructure.",
+        "",
+        "Our solution offers the following key benefits:",
+        "",
+        "  1. Cost reduction of up to 80% on international fax transmissions",
+        "  2. Complete audit trail with encrypted storage for compliance",
+        "  3. Seamless integration with existing PBX and email systems",
+        "  4. Support for T.38 IP fax and traditional PSTN (Class 1/2)",
+        "  5. Multi-language cover pages with OCR verification",
+        "",
+        "This document was transmitted via real POTS lines using the telfax",
+        "open-source fax system running on macOS at V.27ter 4800 bps.",
+        "",
+        "We look forward to discussing this opportunity with you.",
+        "",
+        "Best regards,",
+        "",
+        "Jane Doe",
+        "Chief Technology Officer",
+        "Telfax Corporation",
+    ]
+    y = 780
+    for line in body_text:
+        draw.text((80, y), line, fill=0, font=body_font)
+        y += 52
+
+    # ── Footer ──
+    draw.line([80, y+40, W-80, y+40], fill=180, width=2)
+    draw.text((80, y+60),
+              "Page 1 of 1  |  This fax was transmitted via telfax (opencode.ai)  |  204x196 dpi Fine",
+              fill=120, font=small_font)
+
+    img.save(output_path, dpi=(204, 196))
+    print(f"Demo document created: {output_path}  ({W}x{H} px)")
+
+if __name__ == '__main__':
+    out = sys.argv[1] if len(sys.argv) > 1 else "/tmp/demo_document.tif"
+    create_demo_document(out)