chore(release): cut v1.5.0 changelog

[oss-amikos]

Summary

Cut v1.5.0. The release has one change, #90: IsNull selects row groups whose documents lack the path, whatever the row group's document count (#89). #85 (dependency bumps) is also in this release; earlier changelogs do not list dependency bumps.

 CHANGELOG.md
-## Unreleased
+## v1.5.0 (2026-10-06)

 README.md
-The current wire format is `v11`, written by `v1.2.0`, `v1.3.0` and `v1.4.0`
+The current wire format is `v11`, written by `v1.2.0`, `v1.3.0`, `v1.4.0` and `v1.5.0`

The version is a minor bump. No API is added or removed and the wire format stays v11, but documented IsNull answers change: in one-document row groups and plain 1:1 indexes, IsNull now also selects row groups whose document lacks the key. The result only grows, so pruning stays correct. v1.1.0 shipped the original AbsentRGs rule as a minor bump too.

Evidence

• Before: main at 39deafc has the IsNull misses a row group whose only document lacks the path #89 entries under Unreleased. All 11 CI checks passed on PR fix(query): IsNull selects row groups whose documents lack the path (#89) #90 (darwin/arm64 SIMD on a rerun after a timing smoke-test flake in TestEvaluateWithTracerWithinBudget, unrelated to IsNull).
  After: two text lines differ. No code changes.

Merge Danger

Door: two-way

The merge changes text only. The step after it is one-way: the annotated tag v1.5.0 on main starts release.yml, GoReleaser publishes the GitHub release, and the Go module proxy keeps the version.

Blast Radius: docs