feat: AI flow builder, visibility model, dashboard tabs, fork UI (#88)

- AI flow builder: scaffold → branch detail → assemble → review flow
- Generate All one-click branch generation with stop/cancel
- Regenerate scaffold suggestions button
- 3-action review screen: Start Flow, Open in Editor, Build Another
- Fix Publish button gated behind !isDirty
- Fix visibility column enforcement in tree access filter
- Add ?visibility filter and author_name to GET /trees
- Dashboard tabbed flows: My Flows / My Team / Public / All
- Create button in My Flows tab, window focus reload (stale data fix)
- Fork UI with optional reason modal
- Fix account_id nullability in User type and schema
- Keep is_public and visibility in sync on updates

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

backend/app/core/ai_tree_generator_service.py

@@ -97,7 +97,16 @@ CORRECTIVE_PROMPT_TEMPLATE = """Your previous JSON was invalid for ResolutionFlo
 Validation errors:
 {error_list}
 
-IMPORTANT: If any error mentions a next_node_id referencing a non-existent child, you must ensure every option's next_node_id exactly matches the "id" field of one of the node's direct children. The child node must exist in the "children" array of the same parent node.
+CRITICAL RULES TO FIX THESE ERRORS:
+
+1. Decision node options → next_node_id MUST match the "id" of a direct child in that SAME decision node's "children" array.
+   Example: if decision node has children [A, B, C], then option next_node_id must be "A", "B", or "C".
+
+2. Action node → next_node_id MUST match the "id" of a SIBLING node — another child of the SAME parent decision node.
+   Example: if parent decision has children [action-1, solution-1, solution-2], then action-1's next_node_id must be "solution-1" or "solution-2".
+   The next node must ALREADY EXIST in the parent's children array — do NOT nest the next node inside the action node.
+
+3. Every referenced ID must physically exist somewhere in the tree as a node with that exact "id" value.
 
 Return a corrected full JSON object only. No markdown, no prose, no code fences.
 Fix ALL listed errors while maintaining the same troubleshooting/procedural logic."""
@@ -224,6 +233,12 @@ async def generate_branch_detail(
             len(response.content),
             response.usage.output_tokens,
         )
+        if response.stop_reason == "max_tokens":
+            logger.warning(
+                "branch_detail attempt=%d hit max_tokens limit (%d output tokens) — response may be truncated",
+                attempt,
+                response.usage.output_tokens,
+            )
         raw_text = _strip_markdown_fences(response.content[0].text) if response.content else ""
         if not raw_text:
             logger.warning("branch_detail attempt=%d returned empty text, stop_reason=%s", attempt, response.stop_reason)

backend/app/core/ai_tree_validator.py

@@ -40,7 +40,8 @@ def validate_generated_tree(tree: dict[str, Any]) -> list[str]:
 
     # Collect all node IDs and validate structure
     all_ids: set[str] = set()
-    all_referenced_ids: set[str] = set()
+    all_referenced_ids: set[str] = set()  # option next_node_ids (already checked locally)
+    action_next_ids: set[str] = set()    # action next_node_ids (checked globally below)
     node_count = 0
     solution_count = 0
 
@@ -121,6 +122,7 @@ def validate_generated_tree(tree: dict[str, Any]) -> list[str]:
                 )
             else:
                 all_referenced_ids.add(next_id)
+                action_next_ids.add(next_id)
 
         elif node_type == "solution":
             solution_count += 1
@@ -131,6 +133,13 @@ def validate_generated_tree(tree: dict[str, Any]) -> list[str]:
 
     _validate_node(tree, "root")
 
+    # Check that all action next_node_ids actually exist in the tree
+    for ref_id in action_next_ids:
+        if ref_id not in all_ids:
+            errors.append(
+                f"Action next_node_id '{ref_id}' references a node that does not exist in the tree"
+            )
+
     # Global checks
     if node_count < 5:
         errors.append(

backend/app/core/filters.py

@@ -16,24 +16,32 @@ if TYPE_CHECKING:
 def build_tree_access_filter(current_user: User):
     """Build the access filter for trees based on user permissions.
 
-    Returns trees that are:
-    - All trees (for super admins)
-    - Default/system trees (visible to all)
-    - Public trees
-    - User's own trees
-    - Trees from user's account
+    Visibility rules:
+    - super_admin: sees everything
+    - is_default: visible to all authenticated users
+    - visibility='public': visible to all authenticated users
+    - author_id == me: always visible (regardless of visibility setting)
+    - visibility='team' AND account_id == mine: visible to account members
+    - visibility='private': only visible to author (covered by author_id check above)
+    - visibility='link': only visible to author (share token access is handled separately)
     """
     from app.models.tree import Tree
 
     if current_user.is_super_admin:
         return sa_true()
+
     conditions = [
         Tree.is_default == True,
-        Tree.is_public == True,
+        Tree.visibility == 'public',
         Tree.author_id == current_user.id,
     ]
     if current_user.account_id:
-        conditions.append(Tree.account_id == current_user.account_id)
+        conditions.append(
+            and_(
+                Tree.visibility == 'team',
+                Tree.account_id == current_user.account_id
+            )
+        )
     return or_(*conditions)