Add opencode changeset generator

[markijbema]

Summary

• Add script/opencode-changesets.ts to fetch upstream opencode releases and generate one patch changeset per release in a (from, to] semver range.

in the changelog this results in:

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (4 files)

• .changeset/opencode-v1-14-51-to-v1-15-4.md
• script/upstream/README.md
• script/upstream/opencode-changesets.test.ts
• script/upstream/opencode-changesets.ts

Incremental Changes Since Last Review (b4f9904 → af7228e)

• Bump type changed from minor to patch (all files)
• Added validation that the starting release exists in select()
• Moved head release existence check before range filtering
• Fixed opencode run --agent → kilo run --agent in generated changeset
• Removed "Effect-based core event system" line from generated changeset

Previous Review Summaries (2 snapshots, latest commit b4f9904)

Current summary above is authoritative. Previous snapshots are kept for context only.

Previous review (commit b4f9904)

Status: No Issues Found | Recommendation: Merge

Files Reviewed (4 files)

• .changeset/opencode-v1-14-51-to-v1-15-4.md
• script/upstream/README.md
• script/upstream/opencode-changesets.test.ts
• script/upstream/opencode-changesets.ts

Previous review (commit 01c2593)

Status: No Issues Found | Recommendation: Merge

Files Reviewed (4 files)

• .changeset/opencode-v1-14-51-to-v1-15-4.md
• script/upstream/README.md
• script/upstream/opencode-changesets.test.ts
• script/upstream/opencode-changesets.ts

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_{Reviewed by deepseek-v4-pro-20260423 · 293,748 tokens}

_{Review guidance: REVIEW.md from base branch main}