Add module delete + fail-fast on duplicate module name in wizard.

Delete button lives in module-detail header, refuses to delete a
running module, and clears run_log history first since it doesn't
cascade from module. Wizard now returns 409 on duplicate name before
touching the destination, so a failed resubmit doesn't redundantly
rerun CREATE TABLE / COMMENT ON on the dest.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

pipekit/repo.py

@@ -177,6 +177,26 @@ def list_modules() -> list[dict]:
         return [dict(r) for r in c.execute("SELECT * FROM module ORDER BY name")]
 
 
+class ModuleRunning(RuntimeError):
+    """Raised by delete_module when the module is currently running."""
+
+
+def delete_module(module_id: int) -> bool:
+    """Delete a module and its run_log history. Watermarks, hooks, and
+    group_member rows cascade via FK. Refuses to delete if the module
+    is currently running."""
+    with db.connect() as c:
+        row = c.execute("SELECT running FROM module WHERE id=?",
+                        (module_id,)).fetchone()
+        if row is None:
+            return False
+        if row[0]:
+            raise ModuleRunning(f"module id={module_id} is currently running")
+        c.execute("DELETE FROM run_log WHERE module_id=?", (module_id,))
+        cur = c.execute("DELETE FROM module WHERE id=?", (module_id,))
+        return cur.rowcount > 0
+
+
 def set_next_resolved_query(module_id: int, sql: str) -> None:
     with db.connect() as c:
         c.execute("UPDATE module SET next_resolved_query=?, "

pipekit/web/app.py

@@ -131,6 +131,17 @@ def module_detail(request: Request, module_id: int):
     )
 
 
+@_router.post("/modules/{module_id}/delete")
+def module_delete(module_id: int):
+    if repo.get_module(module_id) is None:
+        raise HTTPException(404, f"module id={module_id} not found")
+    try:
+        repo.delete_module(module_id)
+    except repo.ModuleRunning as e:
+        raise HTTPException(409, str(e))
+    return RedirectResponse(url="/", status_code=303)
+
+
 @_router.post("/modules/{module_id}/run")
 async def module_run_action(module_id: int, request: Request):
     form = await request.form()
@@ -293,6 +304,10 @@ async def wizard_create(request: Request):
     dest_description = (form.get("dest_description") or "").strip() or None
     picked = form.getlist("col")
 
+    if repo.get_module_by_name(module_name) is not None:
+        raise HTTPException(
+            409, f"module name {module_name!r} already exists — pick another")
+
     src_conn = repo.get_connection(source_connection_id)
     if src_conn is None:
         raise HTTPException(404, f"connection id={source_connection_id} not found")

pipekit/web/templates/module_detail.html

@@ -19,6 +19,10 @@
                 <input type="hidden" name="dry_run" value="1">
                 <button type="submit">Dry run</button>
             </form>
+            <form class="inline" method="post" action="/modules/{{ module.id }}/delete"
+                  onsubmit="return confirm('Delete module {{ module.name }}? This removes the module and its run history. The dest table is NOT dropped.')">
+                <button type="submit" class="ghost" style="color:var(--danger)">Delete</button>
+            </form>
         </span>
     </header>
     <div class="body">