docs: add v1.0.38 release notes

[LeXwDeX]

Why

release-fork from main mechanically derives the next stable version from the latest graphagent-v* tag (graphagent-v1.0.37 -> 1.0.38), and the series file .github/releases/v1.0.38.md must exist with exactly that derived-version name or the release job fails closed. This train ships two merged deliveries (#505 resource-leak fix wave, #509 DAG workflow-tool consistency pass) and needs notes per .github/RELEASE_NOTES_TEMPLATE.md.

Scope

• .github/releases/v1.0.38.md only.

Approach

• Draft from the template: keep section order and emoji headings codepoint-identical, omit empty sections, ASCII-only body, required Test Summary (fenced block) and Verification sections, final-line changelog link with {previous_tag}/{current_tag} placeholders.
• Fill content from the two merged deliveries and their review/fix rounds (heap prune ordering fix, parameter snapshot regeneration, the reverted bounded-exit-window attempt recorded on fix: unify child-process stop semantics with await-exit and SIGKILL escalation #503, the SIGTERM-trap readiness race fix in the process test).

Acceptance

• Local render exits 0: bun run ./packages/opencode/script/release-notes.ts --notes-dir .github/releases --version 1.0.38 --channel main --branch main --tag graphagent-v1.0.38 --previous-tag graphagent-v1.0.37 --repo LeXwDeX/OpenCode-GraphAgent --out /tmp/notes.md
• PR gates green; specgit finish exits 0.

[LeXwDeX]

SpecGit delivery branch: docs/510-release-notes-v1-0-38 (draft pull request #511).