Graph: label hubs cluster notes; unlinked notes float by default

Add labels as first-class nodes in the graph so tags act as visual
clustering hubs, and let unlinked notes float in the space by default —
per operator request (the graph is a light auxiliary lens, not a focal
surface).

Backend (graph.py):
- Emit a label-hub node (id "label:<uuid>", kind "label", #name, label
  color) for every label attached to a live note.
- Emit note -> label membership edges (kind "label") alongside the
  existing wiki-link edges (now kind "link").

Frontend (GraphView.vue):
- Render hubs as larger ringed nodes; membership edges dashed with a
  slightly longer spring rest so notes ring their hub.
- Default showAll (unlinked notes float) to true; add a Show labels
  toggle (default on) that hides hubs + membership edges.
- Click a label hub -> that label's board lens (/label/<id>); note
  clicks still open the editor.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

src/thoughtsync/graph.py

@@ -16,10 +16,21 @@ bp = Blueprint("graph", __name__, url_prefix="/api/graph")
 @bp.get("")
 @login_required
 async def get_graph():
-    """Wiki-link graph. Nodes are ALL of the owner's non-trashed notes (the frontend
-    toggles whether to show unlinked ones); each carries its first label's color for
-    clustering. Edges are resolved [[links]] (note_links.target_norm matched to a
-    note's normalized display_title — its explicit title or first body line)."""
+    """Spatial view of the owner's non-trashed notes.
+
+    Nodes are two kinds:
+      - notes (kind="note") — every non-trashed note; each carries its first
+        label's color for tinting.
+      - labels (kind="label", id "label:<uuid>") — every label actually attached
+        to a live note, acting as a clustering HUB so tagged notes gravitate
+        together even without wiki-links between them.
+    Edges are two kinds:
+      - wiki-links (kind="link") — resolved [[links]] (note_links.target_norm
+        matched to a note's normalized display_title).
+      - membership (kind="label") — each note → each of its label hubs.
+    The frontend toggles labels + unlinked notes; the graph is a light auxiliary
+    lens, not a focal surface.
+    """
     source = aliased(Note)
     target = aliased(Note)
     edge_stmt = (
@@ -44,26 +55,51 @@ async def get_graph():
             if key in seen:
                 continue
             seen.add(key)
-            edges.append({"source": str(src_id), "target": str(tgt_id)})
+            edges.append({"source": str(src_id), "target": str(tgt_id), "kind": "link"})
 
-        # First label color per note (labels ordered by name) → node color.
-        color_rows = (
+        # Note ↔ label membership: one row per (note, label) for the owner's
+        # non-trashed notes. Drives both the note-color tint (first label by name)
+        # and the label-hub nodes + membership edges.
+        label_rows = (
             await db.execute(
-                select(NoteLabel.note_id, Label.color)
+                select(NoteLabel.note_id, Label.id, Label.name, Label.color)
                 .join(Label, Label.id == NoteLabel.label_id)
-                .where(Label.owner_id == g.user_id)
+                .join(Note, Note.id == NoteLabel.note_id)
+                .where(
+                    Label.owner_id == g.user_id,
+                    Note.owner_id == g.user_id,
+                    Note.deleted_at.is_(None),
+                )
                 .order_by(Label.name)
             )
         ).all()
+
         first_color: dict = {}
-        for note_id, color in color_rows:
-            first_color.setdefault(note_id, color)
+        label_nodes: dict = {}
+        for note_id, label_id, label_name, label_color in label_rows:
+            first_color.setdefault(note_id, label_color)
+            hub_id = f"label:{label_id}"
+            if hub_id not in label_nodes:
+                label_nodes[hub_id] = {
+                    "id": hub_id,
+                    "title": f"#{label_name}",
+                    "color": label_color or "default",
+                    "kind": "label",
+                    "label_id": str(label_id),
+                }
+            edges.append({"source": str(note_id), "target": hub_id, "kind": "label"})
 
         note_rows = (
             await db.scalars(select(Note).where(Note.owner_id == g.user_id, Note.deleted_at.is_(None)))
         ).all()
         nodes = [
-            {"id": str(n.id), "title": n.display_title or "Untitled", "color": first_color.get(n.id, "default")}
+            {
+                "id": str(n.id),
+                "title": n.display_title or "Untitled",
+                "color": first_color.get(n.id, "default"),
+                "kind": "note",
+            }
             for n in note_rows
         ]
+        nodes.extend(label_nodes.values())
         return jsonify({"nodes": nodes, "edges": edges})