chore: apply fixes after lessons

Author: bartstc

.agents/skills/executing-plans/SKILL.md

@@ -34,7 +34,7 @@ Collaborate with the developer to fill sections 1-3 of the template.
 
 Collaborate on sections 4-6 of the template.
 
-1. Propose a **Building Blocks Diff** — list every block that is ADDED, MODIFIED, or DELETED. Use the project's building block taxonomy from `.agents/skills/building-blocks/SKILL.md` (mutation-hook, query-options-factory, store, use-case-hook, pure-component, compound-component, page, facade-hook, frontend-model, value-object, etc.). Reference by **name and type only** — do not define internals. Implementation details belong in coding standards and per-type skills, not specs. For changes that don't map to a typed building block, use the target file path + a short description instead.
+1. Propose a **Building Blocks Diff** — list every block that is ADDED, MODIFIED, or DELETED. Use the project's building block taxonomy from `.agents/skills/building-blocks/SKILL.md`. Reference by **name and type only** — do not define internals. Implementation details belong in coding standards and per-type skills, not specs. For changes that don't map to a typed building block, use the target file path + a short description instead.
 2. For non-trivial features, propose **two plausible designs** with tradeoffs. Let the developer choose. Capture the winner and rationale in **Design Decisions**
 3. Draft the **Boundaries** section using the three-tier system:
    - ✅ **Always** — proceed without asking (e.g., create files in the feature directory)

.agents/skills/writing-spec/SKILL.md

@@ -53,6 +53,7 @@ Each feature follows feature slice architecture patterns with four layers:
 - **components/** - UI components, presentational and decoupled from business logic (application) and router state. Data access is only through `providers/`.
 - **application/** - Business logic, portable state management (stores, FSMs, form validation), custom hooks. Should not depend on router state or external APIs directly (only through `providers/`).
 - **providers/** - Hook composition and data access gateway for the feature slice. Exposes query hooks, mutations, loaders, domain errors, and DTOs sourced from `src/lib/api/`. Library-specific code (React Query, etc.) must not leak beyond this layer.
+  - files are named after their primary export or reexport: `useCartProductsQuery` → `use-cart-products-query.ts`, `useAddToCartMutation` → `use-add-to-cart-mutation.ts`
 - **models/** - Domain type definitions, utilities, and type mapping functions.
 
 **Dependency rule:** `components/` and `application/` import from `models/` and `providers/`. `providers/` and `models/` have no internal feature dependencies.

docs/architecture.md

@@ -0,0 +1,19 @@
+# Lessons Learned
+
+Patterns captured after corrections. Review at session start.
+
+## Template
+
+```markdown
+## L<NNN> — <short title>
+
+**Rule:** <the rule to follow going forward>
+
+**Why it failed:** <what caused the mistake>
+
+**How to apply:** <concrete guidance for when/where this kicks in>
+
+**Source:** <context — spec, PR, correction date>
+```
+
+---