chore: bump .node-version to 26.5.1

[jdalton]

Bumps the pinned dev/CI Node from 26.5.0 to 26.5.1 (latest stable).

.node-version is perry's Node pin — CI consumes it via actions/setup-node's node-version-file: .node-version (test.yml, feature-matrix, node-suite-guard, security-audit, …), and local fnm/nodenv/asdf pick it up. This aligns it with the compat-matrix oracle pinned at 26.5.1 in external-tools.json (added in #7074), so the Node that builds perry and the Node it's measured against no longer skew by a patch.

Summary by CodeRabbit

• Chores
  • Updated the project’s pinned Node.js version to 26.5.1.
• Documentation
  • Added a changelog entry documenting the Node.js version update.

[coderabbitai]

📝 Walkthrough

Walkthrough

The pinned Node.js version changes from 26.5.0 to 26.5.1, and a changelog entry documents the update and its alignment with the compatibility matrix.

Changes

Node.js version update

Layer / File(s)	Summary
Update pinned Node.js version .node-version, changelog.d/0000-node-version-26.5.1.md	The configured development and CI Node.js version changes to 26.5.1, with a changelog entry documenting the update.

Estimated code review effort: 1 (Trivial) | ~2 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description explains the change, but it misses the required template sections like Summary, Changes, Related issue, Test plan, and Checklist.	Reformat it to the repo template and add Summary, Changes, Related issue, Test plan, Screenshots/output, and Checklist entries.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately reflects the Node version bump in the change set.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@changelog.d/0000-node-version-26.5.1.md`:
- Line 1: Rename the changelog fragment from the 0000-prefixed filename to
changelog.d/<actual-PR-number>-node-version-26.5.1.md, preserving its existing
content and omitting any version header.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: be6e3bd5-3d7d-400f-b38d-0c91af576008

📥 Commits

Reviewing files that changed from the base of the PR and between 9a3967b and eadce3c.

📒 Files selected for processing (2)

• .node-version
• changelog.d/0000-node-version-26.5.1.md

[coderabbitai]

📐 Maintainability & Code Quality | 🟠 Major | ⚡ Quick win

Use the actual PR number in the changelog filename.

Rename this file to changelog.d/<PR>-node-version-26.5.1.md; 0000 does not satisfy the required PR-keyed fragment convention. As per coding guidelines, changelog fragments must use changelog.d/<PR>-<slug>.md without a version header.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@changelog.d/0000-node-version-26.5.1.md` at line 1, Rename the changelog
fragment from the 0000-prefixed filename to
changelog.d/<actual-PR-number>-node-version-26.5.1.md, preserving its existing
content and omitting any version header.

Source: Coding guidelines