feat: Add initial PostgreSQL best practices rules (#1)

* Add 30 PostgreSQL best practices rules

Rules organized in 8 categories:
- Query Performance (5): indexes, partial indexes, composite, covering, types
- Connection Management (4): pooling, limits, idle timeout, prepared statements
- Schema Design (4): data types, primary keys, foreign key indexes, partitioning
- Concurrency & Locking (4): short transactions, SKIP LOCKED, advisory, deadlocks
- Security (3): RLS basics, RLS performance, privileges
- Data Access Patterns (4): N+1 queries, pagination, upsert, batch inserts
- Monitoring (3): EXPLAIN ANALYZE, pg_stat_statements, VACUUM/ANALYZE
- Advanced Features (3): JSONB indexing, full-text search, CTE materialization

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* Update skills/postgresql-best-practices/rules/schema-primary-keys.md

Co-authored-by: samrose <samuel.rose@gmail.com>

* Update skills/postgresql-best-practices/rules/lock-deadlock-prevention.md

Co-authored-by: samrose <samuel.rose@gmail.com>

* resolve merge conflicts from postgres team suggestions

* Delete GETTING_STARTED.md

* Restore all 30 rule files that were lost during rebase

* update agents.md

* remove postgres 11 mention to advanced cte optimization

* update agents.md

* replace advanced cte with check contraints

* replace check contraints with schema lowercase identifiers

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: samrose <samuel.rose@gmail.com>

skills/postgres-best-practices/rules/lock-skip-locked.md

@@ -0,0 +1,54 @@
+---
+title: Use SKIP LOCKED for Non-Blocking Queue Processing
+impact: MEDIUM-HIGH
+impactDescription: 10x throughput for worker queues
+tags: skip-locked, queue, workers, concurrency
+---
+
+## Use SKIP LOCKED for Non-Blocking Queue Processing
+
+When multiple workers process a queue, SKIP LOCKED allows workers to process different rows without waiting.
+
+**Incorrect (workers block each other):**
+
+```sql
+-- Worker 1 and Worker 2 both try to get next job
+begin;
+select * from jobs where status = 'pending' order by created_at limit 1 for update;
+-- Worker 2 waits for Worker 1's lock to release!
+```
+
+**Correct (SKIP LOCKED for parallel processing):**
+
+```sql
+-- Each worker skips locked rows and gets the next available
+begin;
+select * from jobs
+where status = 'pending'
+order by created_at
+limit 1
+for update skip locked;
+
+-- Worker 1 gets job 1, Worker 2 gets job 2 (no waiting)
+
+update jobs set status = 'processing' where id = $1;
+commit;
+```
+
+Complete queue pattern:
+
+```sql
+-- Atomic claim-and-update in one statement
+update jobs
+set status = 'processing', worker_id = $1, started_at = now()
+where id = (
+  select id from jobs
+  where status = 'pending'
+  order by created_at
+  limit 1
+  for update skip locked
+)
+returning *;
+```
+
+Reference: [SELECT FOR UPDATE SKIP LOCKED](https://www.postgresql.org/docs/current/sql-select.html#SQL-FOR-UPDATE-SHARE)