docs(changelog): add Story 36.5 nightly CI entry to [Unreleased]

[ALLiDoizCode]

Problem

npm publish (triggered by the v3.5.1 release in run #25521561656) failed in prepublishOnly → npm test:

FAIL test/integration/story-36-5-nightly-ci-validation.test.ts
  ● AC 14: CHANGELOG + sprint-status updates (Story 36.5)
    › CHANGELOG.md has a 36.5 entry under [Unreleased]

    expect(received).toMatch(expected)
    Expected pattern: /36[.-]5/
    Received string:  "### Build\n- Multi-arch image..."

Root cause chain:

1. PR ci(release): build linux/arm64 alongside amd64 for connector + ATOR sidecar #63 added ## [Unreleased] with only the multi-arch build note
2. PR fix(ci): fix imagetools verify for multi-arch manifest index #64's fix: commit triggered a v3.5.1 release → npm publish → prepublishOnly → npm test
3. story-36-5-nightly-ci-validation.test.ts AC 14 checks that [Unreleased] matches /36[.-]5/ and /nightly/i
4. The multi-arch Build note satisfies neither pattern → test fails → publish fails

Story 36.5's AC 14 required a ### Added entry referencing the nightly-ator workflow. That entry was missing from [Unreleased].

Fix

Add the Story 36.5 nightly CI entry under ### Added in [Unreleased], alongside the existing multi-arch ### Build note.

Why docs: commit type

docs: maps to release: false in .releaserc.json — no version bump, no new release, no npm publish triggered. The next organic feat/fix release will run prepublishOnly with the corrected [Unreleased] section and the AC 14 test will pass.

[github-actions]

🎉 This PR is included in version 3.6.0 🎉

The release is available on GitHub release

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