chore(opencode): update overlay to v1.18.8

[fredclausen]

Automated bump of the opencode overlay (see overlays/opencode.nix) to the latest upstream release. Verified locally: nix build .#nixosConfigurations.Daytona.pkgs.opencode succeeds.

Summary by CodeRabbit

• Updates
  • Updated the bundled OpenCode release from version 1.18.6 to 1.18.8.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 00a56c7f-4c2e-4665-ad36-aaa2fef87c45

📥 Commits

Reviewing files that changed from the base of the PR and between 8acc80b and 1bcba1a.

📒 Files selected for processing (1)

• overlays/opencode.nix

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📝 Walkthrough

Walkthrough

The opencode overlay updates the pinned upstream release from 1.18.6 to 1.18.8, including its GitHub source hash and fixed-output node_modules hash.

Changes

Opencode release update

Layer / File(s)	Summary
Update opencode package pin overlays/opencode.nix	The opencode version, GitHub source tag and hash, and node_modules fixed-output hash are updated to release 1.18.8.

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

Possibly related PRs

• fredsystems/nixos#1975: Updates the same opencode version, source hash, and node_modules output hash.
• fredsystems/nixos#2073: Applies the same overlay update pattern for an earlier opencode release.
• fredsystems/nixos#2085: Updates the same opencode overlay and fixed-output dependency hash.

Suggested reviewers: web-flow

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: updating the opencode overlay to v1.18.8.
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
• Commit unit tests in branch update-opencode-1.18.8

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