Initial import from garrytan/gstack@026751e (main snapshot via local relay)

Source: https://github.com/garrytan/gstack/commit/026751e

review/specialists/performance.md

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+# Performance Specialist Review Checklist
+
+Scope: When SCOPE_BACKEND=true OR SCOPE_FRONTEND=true
+Output: JSON objects, one finding per line. Schema:
+{"severity":"CRITICAL|INFORMATIONAL","confidence":N,"path":"file","line":N,"category":"performance","summary":"...","fix":"...","fingerprint":"path:line:performance","specialist":"performance"}
+Optional: line, fix, fingerprint, evidence, test_stub.
+If no findings: output `NO FINDINGS` and nothing else.
+
+---
+
+## Categories
+
+### N+1 Queries
+- ActiveRecord/ORM associations traversed in loops without eager loading (.includes, joinedload, include)
+- Database queries inside iteration blocks (each, map, forEach) that could be batched
+- Nested serializers that trigger lazy-loaded associations
+- GraphQL resolvers that query per-field instead of batching (check for DataLoader usage)
+
+### Missing Database Indexes
+- New WHERE clauses on columns without indexes (check migration files or schema)
+- New ORDER BY on non-indexed columns
+- Composite queries (WHERE a AND b) without composite indexes
+- Foreign key columns added without indexes
+
+### Algorithmic Complexity
+- O(n^2) or worse patterns: nested loops over collections, Array.find inside Array.map
+- Repeated linear searches that could use a hash/map/set lookup
+- String concatenation in loops (use join or StringBuilder)
+- Sorting or filtering large collections multiple times when once would suffice
+
+### Bundle Size Impact (Frontend)
+- New production dependencies that are known-heavy (moment.js, lodash full, jquery)
+- Barrel imports (import from 'library') instead of deep imports (import from 'library/specific')
+- Large static assets (images, fonts) committed without optimization
+- Missing code splitting for route-level chunks
+
+### Rendering Performance (Frontend)
+- Fetch waterfalls: sequential API calls that could be parallel (Promise.all)
+- Unnecessary re-renders from unstable references (new objects/arrays in render)
+- Missing React.memo, useMemo, or useCallback on expensive computations
+- Layout thrashing from reading then writing DOM properties in loops
+- Missing loading="lazy" on below-fold images
+
+### Missing Pagination
+- List endpoints that return unbounded results (no LIMIT, no pagination params)
+- Database queries without LIMIT that grow with data volume
+- API responses that embed full nested objects instead of IDs with expansion
+
+### Blocking in Async Contexts
+- Synchronous I/O (file reads, subprocess, HTTP requests) inside async functions
+- time.sleep() / Thread.sleep() inside event-loop-based handlers
+- CPU-intensive computation blocking the main thread without worker offload