Refactor canvas storage URL handling and integrate adjustment presets

- Introduced a new `CanvasPresetsProvider` to manage adjustment presets for nodes, enhancing state management and reducing reactivity.
- Updated storage URL resolution to utilize a mutation instead of a reactive query, improving performance and reducing unnecessary re-renders.
- Refactored adjustment nodes (color-adjust, curves, detail-adjust, light-adjust) to use the new preset context for fetching user presets.
- Improved overall canvas functionality by streamlining storage ID collection and URL resolution processes.

docs/plans/2026-04-03-canvas-convex-load-shedding.md

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+# Canvas Convex Load Shedding Implementation Plan
+
+> **For Claude:** REQUIRED SUB-SKILL: Use superpowers:executing-plans to implement this plan task-by-task.
+
+**Goal:** Reduce Convex canvas-page load by removing non-essential hot-path queries and collapsing redundant read models.
+
+**Architecture:** The canvas keeps `nodes:list`, `edges:list`, and `canvases:get` as the primary real-time model while shedding secondary reads. Storage URLs move to a client-derived fallback path, presets move to a shared context backed by one query, and the toolbar stops depending on the subscription query.
+
+**Tech Stack:** Next.js 16, React 19, Convex, React Flow, TypeScript
+
+---
+
+### Task 1: Remove unnecessary canvas hot-path queries
+
+**Files:**
+- Modify: `components/canvas/canvas.tsx`
+- Modify: `components/canvas/credit-display.tsx`
+- Modify: `components/canvas/canvas-toolbar.tsx`
+
+**Step 1:** Remove the debug-only `api.auth.safeGetAuthUser` query from `components/canvas/canvas.tsx`.
+
+**Step 2:** Remove `api.credits.getSubscription` dependency from `components/canvas/credit-display.tsx` and keep the widget on the balance query only.
+
+**Step 3:** Update toolbar rendering only as needed to match the leaner credit widget.
+
+### Task 2: Remove server-side storage URL batching from the canvas hot path
+
+**Files:**
+- Modify: `components/canvas/canvas.tsx`
+- Modify: `lib/canvas-utils.ts`
+
+**Step 1:** Stop subscribing to `api.storage.batchGetUrlsForCanvas` from the canvas page.
+
+**Step 2:** Extend `convexNodeDocWithMergedStorageUrl` to synthesize a stable fallback URL from `storageId` when no cached URL exists.
+
+**Step 3:** Preserve previous merged URLs when available so existing anti-flicker behavior remains intact.
+
+### Task 3: Collapse preset reads into one shared query
+
+**Files:**
+- Create: `components/canvas/canvas-presets-context.tsx`
+- Modify: `components/canvas/canvas.tsx`
+- Modify: `components/canvas/nodes/curves-node.tsx`
+- Modify: `components/canvas/nodes/color-adjust-node.tsx`
+- Modify: `components/canvas/nodes/light-adjust-node.tsx`
+- Modify: `components/canvas/nodes/detail-adjust-node.tsx`
+
+**Step 1:** Add a shared presets provider that executes one `api.presets.list` query.
+
+**Step 2:** Filter presets client-side by node type via a small hook/helper.
+
+**Step 3:** Replace per-node `useAuthQuery(api.presets.list, { nodeType })` calls with the shared presets hook.
+
+### Task 4: Verify the refactor
+
+**Files:**
+- Verify only
+
+**Step 1:** Run lint on touched files.
+
+**Step 2:** Run targeted type-check or full type-check if feasible.
+
+**Step 3:** Reproduce canvas placement flow and confirm Convex hot-path query count is reduced.