feat(ci): extract changelog generation script and use for draft releases

- Create script/generate-changelog.ts with reusable changelog generation logic
- Update ci.yml draft-release job to use the new script instead of GitHub's generate-notes API
- Ensures draft release notes follow the same format as published releases

🤖 Generated with assistance of oh-my-opencode

script/generate-changelog.ts

@@ -0,0 +1,92 @@
+#!/usr/bin/env bun
+
+import { $ } from "bun"
+
+const TEAM = ["actions-user", "github-actions[bot]", "code-yeongyu"]
+
+async function getLatestReleasedTag(): Promise<string | null> {
+  try {
+    const tag = await $`gh release list --exclude-drafts --exclude-pre-releases --limit 1 --json tagName --jq '.[0].tagName // empty'`.text()
+    return tag.trim() || null
+  } catch {
+    return null
+  }
+}
+
+async function generateChangelog(previousTag: string): Promise<string[]> {
+  const notes: string[] = []
+
+  try {
+    const log = await $`git log ${previousTag}..HEAD --oneline --format="%h %s"`.text()
+    const commits = log
+      .split("\n")
+      .filter((line) => line && !line.match(/^\w+ (ignore:|test:|chore:|ci:|release:)/i))
+
+    if (commits.length > 0) {
+      for (const commit of commits) {
+        notes.push(`- ${commit}`)
+      }
+    }
+  } catch {
+    // No previous tags found
+  }
+
+  return notes
+}
+
+async function getContributors(previousTag: string): Promise<string[]> {
+  const notes: string[] = []
+
+  try {
+    const compare =
+      await $`gh api "/repos/code-yeongyu/oh-my-opencode/compare/${previousTag}...HEAD" --jq '.commits[] | {login: .author.login, message: .commit.message}'`.text()
+    const contributors = new Map<string, string[]>()
+
+    for (const line of compare.split("\n").filter(Boolean)) {
+      const { login, message } = JSON.parse(line) as { login: string | null; message: string }
+      const title = message.split("\n")[0] ?? ""
+      if (title.match(/^(ignore:|test:|chore:|ci:|release:)/i)) continue
+
+      if (login && !TEAM.includes(login)) {
+        if (!contributors.has(login)) contributors.set(login, [])
+        contributors.get(login)?.push(title)
+      }
+    }
+
+    if (contributors.size > 0) {
+      notes.push("")
+      notes.push(`**Thank you to ${contributors.size} community contributor${contributors.size > 1 ? "s" : ""}:**`)
+      for (const [username, userCommits] of contributors) {
+        notes.push(`- @${username}:`)
+        for (const commit of userCommits) {
+          notes.push(`  - ${commit}`)
+        }
+      }
+    }
+  } catch {
+    // Failed to fetch contributors
+  }
+
+  return notes
+}
+
+async function main() {
+  const previousTag = await getLatestReleasedTag()
+
+  if (!previousTag) {
+    console.log("Initial release")
+    process.exit(0)
+  }
+
+  const changelog = await generateChangelog(previousTag)
+  const contributors = await getContributors(previousTag)
+  const notes = [...changelog, ...contributors]
+
+  if (notes.length === 0) {
+    console.log("No notable changes")
+  } else {
+    console.log(notes.join("\n"))
+  }
+}
+
+main()