feat: initial project setup with gai tool

src/prompt.ts

@@ -0,0 +1,56 @@
+import type { ProjectContext } from "./types";
+
+export const SYSTEM_PROMPT = `You are an expert at writing concise, meaningful git commit messages following the Conventional Commits specification.
+
+Format: <type>(<scope>): <description>
+
+Types: feat, fix, docs, style, refactor, perf, test, build, ci, chore, revert
+
+Rules:
+1. Use imperative mood in description (e.g., "add feature" not "added feature")
+2. Keep the first line (subject) under 72 characters
+3. Scope is optional but recommended when the change area is clear
+4. For breaking changes, add "!" after the scope: feat(scope)!: description
+5. If the change needs explanation, add a body separated by a blank line — explain WHY, not WHAT
+6. Match the language and style of recent commits if provided
+7. Be specific — avoid vague messages like "update code" or "fix bugs"
+8. Output ONLY the commit message text, no markdown, no code blocks, no prefixes`;
+
+export function buildPrompt(context: ProjectContext): string {
+  const parts: string[] = [];
+
+  if (
+    context.packageDescription ||
+    context.readme ||
+    context.structure
+  ) {
+    parts.push("## Project Context");
+    if (context.packageDescription) {
+      parts.push(`Description: ${context.packageDescription}`);
+    }
+    if (context.structure) {
+      parts.push(`Structure: ${context.structure}`);
+    }
+    if (context.readme) {
+      parts.push(`README:\n${context.readme}`);
+    }
+    parts.push("");
+  }
+
+  if (context.recentCommits.length > 0) {
+    parts.push("## Recent Commits (for style reference)");
+    for (const c of context.recentCommits) {
+      parts.push(c);
+    }
+    parts.push("");
+  }
+
+  parts.push("## Staged Changes");
+  parts.push("```diff");
+  parts.push(context.diff);
+  parts.push("```");
+  parts.push("");
+  parts.push("Generate a commit message for the above changes.");
+
+  return parts.join("\n");
+}