Force-directed graph view with tag nodes, project clustering, physics tuning

- New /graph route with D3 force simulation (GraphView.vue)
- Tag nodes as first-class graph nodes (string IDs "tag:name") — clicking
  navigates to /notes?tags=name; tags shown by default
- Invisible project hub nodes attract project members into clusters
- Physics panel with live sliders: repulsion, link distance, link strength,
  project pull, gravity (forceX/forceY, not forceCenter)
- Wikilink edges retain directed arrowheads; tag edges are thin, no arrowhead
- Graph nav link in AppHeader; `g` shortcut in App.vue
- Backend: build_note_graph() emits tag nodes + note→tag edges instead of
  O(n²) note→note shared-tag mesh

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/fabledassistant/routes/notes.py

@@ -17,6 +17,7 @@ from fabledassistant.services.generation_buffer import (
 )
 from fabledassistant.services.generation_task import run_assist_generation
 from fabledassistant.services.notes import (
+    build_note_graph,
     convert_note_to_task,
     convert_task_to_note,
     create_note,
@@ -510,3 +511,15 @@ async def get_version_route(note_id: int, version_id: int):
     if version is None:
         return not_found("Version")
     return jsonify(version.to_dict(include_body=True))
+
+
+# ── Graph route ────────────────────────────────────────────────────────────────
+
+@notes_bp.route("/graph", methods=["GET"])
+@login_required
+async def graph_route():
+    uid = get_current_user_id()
+    project_id = request.args.get("project_id", type=int)
+    shared_tags = request.args.get("shared_tags", "false").lower() == "true"
+    graph = await build_note_graph(uid, project_id=project_id, include_shared_tags=shared_tags)
+    return jsonify(graph)

src/fabledassistant/services/notes.py

@@ -1,4 +1,5 @@
 import logging
+import re
 from datetime import date, datetime, timezone
 
 from sqlalchemy import func, or_, select, text
@@ -356,3 +357,82 @@ async def get_backlinks(user_id: int, note_id: int) -> list[dict]:
             backlinks.append({"type": link_type, "id": row[0], "title": row[1]})
 
         return backlinks
+
+
+_WIKILINK_RE = re.compile(r'\[\[([^\]|]+)(?:\|[^\]]+)?\]\]')
+
+
+async def build_note_graph(
+    user_id: int,
+    project_id: int | None = None,
+    include_shared_tags: bool = False,
+) -> dict:
+    notes, _ = await list_notes(user_id, project_id=project_id, limit=1000)
+    if not notes:
+        return {"nodes": [], "edges": []}
+
+    # Fetch project colours
+    project_ids = {n.project_id for n in notes if n.project_id is not None}
+    project_colors: dict[int, str] = {}
+    if project_ids:
+        from fabledassistant.models.project import Project
+        async with async_session() as session:
+            result = await session.execute(
+                select(Project.id, Project.color).where(Project.id.in_(project_ids))
+            )
+            for pid, color in result.fetchall():
+                project_colors[pid] = color or "#888888"
+
+    # Build title lookup (lowercase → id)
+    title_map: dict[str, int] = {}
+    for n in notes:
+        if n.title:
+            title_map[n.title.lower()] = n.id
+
+    # Build nodes
+    nodes = []
+    for n in notes:
+        nodes.append({
+            "id": n.id,
+            "title": n.title or "(untitled)",
+            "type": "task" if n.is_task else "note",
+            "tags": n.tags or [],
+            "project_id": n.project_id,
+            "project_color": project_colors.get(n.project_id) if n.project_id else None,
+        })
+
+    # Build wikilink edges
+    edge_set: set[tuple[int, int]] = set()
+    edges = []
+    for n in notes:
+        if not n.body:
+            continue
+        for match in _WIKILINK_RE.findall(n.body):
+            target_id = title_map.get(match.strip().lower())
+            if target_id is not None and target_id != n.id:
+                pair = (n.id, target_id)
+                if pair not in edge_set:
+                    edge_set.add(pair)
+                    edges.append({"source": n.id, "target": target_id, "type": "wikilink"})
+
+    # Build tag nodes + note→tag edges
+    if include_shared_tags:
+        tag_to_ids: dict[str, list[int]] = {}
+        for n in notes:
+            for tag in (n.tags or []):
+                tag_to_ids.setdefault(tag, []).append(n.id)
+
+        for tag, note_ids in tag_to_ids.items():
+            tag_node_id = f"tag:{tag}"
+            nodes.append({
+                "id": tag_node_id,
+                "title": tag,
+                "type": "tag",
+                "tags": [],
+                "project_id": None,
+                "project_color": None,
+            })
+            for nid in note_ids:
+                edges.append({"source": nid, "target": tag_node_id, "type": "tag"})
+
+    return {"nodes": nodes, "edges": edges}