docs: add release notes for 7.0

Author: NikolayS

RELEASE_NOTES.md

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+# postgres_dba 7.0
+
+**30 reports** | Tested on **PostgreSQL 13–18** | Works with `pg_monitor` role
+
+## New Reports
+
+### b6 — Buffer cache contents
+What's in your `shared_buffers` right now. Shows cached size vs total size, % of cache used per object, and dirty buffer counts. Requires `pg_buffercache` extension.
+
+### s3 — Workload profile by query type
+Groups `pg_stat_statements` by first SQL keyword (SELECT, INSERT, UPDATE, DELETE, etc.) to show workload composition at a glance. Correctly handles queries with leading block comments (`/* ... */`) and line comments (`-- ...`).
+
+### t2 — Objects with custom storage parameters
+Lists all tables, indexes, and materialized views with non-default `reloptions`. Flags potentially problematic settings: disabled autovacuum on large tables, low fillfactor, aggressive vacuum scale factors. Shows partition relationships.
+
+### Report 0 — WAL and replication slot info
+The node information report now includes:
+- **WAL**: current LSN, file count, total WAL size
+- **Replication Slots**: name, type, active/inactive status, lag from current WAL position
+
+## Bug Fixes
+
+- **i3**: Fixed `operator is not unique` error when `intarray` extension is installed (added explicit `::int2[]` cast)
+- **s1, s2**: Fixed `blk_read_time does not exist` error on PostgreSQL 17+ (`blk_read_time`/`blk_write_time` renamed to `shared_blk_read_time`/`shared_blk_write_time` in pg_stat_statements 1.11)
+- **i2**: Removed unused `redundant_indexes_grouped` CTE (dead code)
+- **s1**: Removed duplicate `sum(calls)` in the pre-PG13 code path
+
+## Terminology
+
+- Updated `Master` → `Primary` across all reports and CI (0_node, i2, i4, i5)
+
+## Typo Fixes
+
+- `inspect` → `inspects` (b1, b2)
+- `filed` → `fields`, `fractionnal` → `fractional`, `functionnal` → `functional` (b2)
+- `alt_shits` → `alt_shifts` (p1) 🙈
+- `Vaccuum` → `Vacuum` (b1)
+- `format` → `formatting` (s2)
+- Comment formatting: added space after `--` throughout (b3, b4, l1, s2, v2)
+
+## CI Improvements
+
+- Added `PAGER=cat` to all `psql` invocations (prevents pager hangs)
+- Added `intarray` and `pg_buffercache` extensions to test matrix
+- Added foreign key test tables for i3 regression testing
+- Added dedicated i3 regression test with `intarray` installed
+
+## Compatibility
+
+Tested on PostgreSQL 13, 14, 15, 16, 17, and 18 — all 30 reports pass with both superuser and `pg_monitor` roles.