feat: welcome.canvas — visual demo board + default first tab

Three-act visual story:
  [Drop Sources] → [I Process] → [Your Brain Grows]

Zone 1 'Drop Your Sources' (green):
  '📸 Paste any images — I will take care of the rest'
  Example: claude-seo-cover.png + hub-cover.png + blog-cover.png
  '📄 Drop PDFs & Markdown with easy drag & drop'

Zone 2 'I Process Everything' (orange):
  workflow-loop.gif (animated 4-step cycle)
  'Reads sources → extracts → cross-references → files'

Zone 3 'Your Brain (Vault) Grows' (purple):
  '🧠 I'll create a full map/brain for you'
  wiki-graph-grow.gif (animated knowledge graph growing)
  'Cross-referenced. Searchable. Gets richer every session.'

4 callouts: 8-15 pages / hot cache / query anything / visual map

2 labeled arrows: ingest → builds

workspace.json: welcome.canvas is now the first tab (default view)
  Tab 1: welcome.canvas (active on open)
  Tab 2: main.canvas

wiki/canvases/welcome.canvas

@@ -0,0 +1,141 @@
+{
+  "nodes": [
+
+    {
+      "id": "main-title",
+      "type": "text",
+      "text": "# 🧠 Cosmic Brain\n### Drop anything. I'll build your knowledge base.",
+      "x": -420, "y": -560, "width": 840, "height": 110
+    },
+    {
+      "id": "sub-title",
+      "type": "text",
+      "text": "Images · PDFs · Markdown · Transcripts · URLs — drag, drop, or paste. I handle the rest.",
+      "x": -420, "y": -440, "width": 840, "height": 54, "color": "5"
+    },
+
+    {
+      "id": "zone-input",
+      "type": "group",
+      "label": "1 · Drop Your Sources",
+      "x": -680, "y": -360, "width": 560, "height": 560, "color": "4"
+    },
+    {
+      "id": "text-drop-images",
+      "type": "text",
+      "text": "## 📸 Paste any image here\n\nHere you can paste any images and I will take care of the rest.",
+      "x": -660, "y": -340, "width": 520, "height": 110, "color": "4"
+    },
+    {
+      "id": "example-img-1",
+      "type": "file",
+      "file": "_attachments/images/skool-hub/claude-seo-cover.png",
+      "x": -660, "y": -220, "width": 420, "height": 216
+    },
+    {
+      "id": "text-drop-pdf",
+      "type": "text",
+      "text": "## 📄 Or drop PDF & Markdown files\n\nJust easy drag & drop — I'll extract everything.",
+      "x": -660, "y": 10, "width": 520, "height": 100, "color": "4"
+    },
+    {
+      "id": "example-img-2",
+      "type": "file",
+      "file": "_attachments/images/skool-hub/hub-cover.png",
+      "x": -660, "y": 120, "width": 260, "height": 134
+    },
+    {
+      "id": "example-img-3",
+      "type": "file",
+      "file": "_attachments/images/skool-hub/claude-blog-cover.png",
+      "x": -380, "y": 120, "width": 160, "height": 160
+    },
+
+    {
+      "id": "zone-process",
+      "type": "group",
+      "label": "2 · I Process Everything",
+      "x": -60, "y": -360, "width": 480, "height": 560, "color": "2"
+    },
+    {
+      "id": "gif-workflow",
+      "type": "file",
+      "file": "wiki/meta/workflow-loop.gif",
+      "x": -40, "y": -340, "width": 440, "height": 440
+    },
+    {
+      "id": "text-process",
+      "type": "text",
+      "text": "Reads sources → extracts entities & concepts → cross-references everything → files it all automatically.",
+      "x": -40, "y": 110, "width": 440, "height": 80, "color": "2"
+    },
+
+    {
+      "id": "zone-output",
+      "type": "group",
+      "label": "3 · Your Brain (Vault) Grows",
+      "x": 480, "y": -360, "width": 560, "height": 560, "color": "6"
+    },
+    {
+      "id": "text-brain",
+      "type": "text",
+      "text": "## 🧠 I'll create a full map/brain for you\n\nEvery source compounds the knowledge base.",
+      "x": 500, "y": -340, "width": 520, "height": 100, "color": "6"
+    },
+    {
+      "id": "gif-graph",
+      "type": "file",
+      "file": "wiki/meta/wiki-graph-grow.gif",
+      "x": 500, "y": -230, "width": 420, "height": 420
+    },
+    {
+      "id": "text-result",
+      "type": "text",
+      "text": "Cross-referenced. Searchable. Gets richer every session.",
+      "x": 500, "y": 200, "width": 520, "height": 50, "color": "6"
+    },
+
+    {
+      "id": "callout-1",
+      "type": "text",
+      "text": "💡 **8–15 wiki pages**\nper source ingested",
+      "x": -680, "y": 260, "width": 260, "height": 80, "color": "4"
+    },
+    {
+      "id": "callout-2",
+      "type": "text",
+      "text": "⚡ **Hot cache**\ninstant session context",
+      "x": -400, "y": 260, "width": 260, "height": 80, "color": "2"
+    },
+    {
+      "id": "callout-3",
+      "type": "text",
+      "text": "🔍 **Query anything**\nyou've ever added",
+      "x": -120, "y": 260, "width": 260, "height": 80, "color": "5"
+    },
+    {
+      "id": "callout-4",
+      "type": "text",
+      "text": "🕸️ **Visual map**\nFibonacci graph layout",
+      "x": 160, "y": 260, "width": 260, "height": 80, "color": "6"
+    }
+
+  ],
+
+  "edges": [
+    {
+      "id": "arrow-1",
+      "fromNode": "zone-input", "fromSide": "right",
+      "toNode": "zone-process", "toSide": "left",
+      "toEnd": "arrow", "color": "4",
+      "label": "ingest"
+    },
+    {
+      "id": "arrow-2",
+      "fromNode": "zone-process", "fromSide": "right",
+      "toNode": "zone-output", "toSide": "left",
+      "toEnd": "arrow", "color": "6",
+      "label": "builds"
+    }
+  ]
+}