refactor(prompts): extract prompts to dedicated module and enhance instructions

src/prompts.ts

@@ -0,0 +1,26 @@
+export const SYSTEM_PROMPT =
+  "You are a git commit message generator. Output only the commit message — no explanation, no preamble, no backticks, no quotes. All messages must be written in English."
+
+export const CONVENTIONAL_INSTRUCTION = `Based on the provided git diff, generate a concise and descriptive commit message following the Conventional Commits format:
+
+  <type>(<scope>): <short description>
+
+Types: feat, fix, refactor, style, docs, test, chore, perf, revert
+- feat: new feature
+- fix: bug fix
+- refactor: code restructuring without behavior change
+- style: formatting only (spaces, commas, no logic change)
+- docs: documentation only
+- test: add or update tests
+- chore: maintenance, dependencies, build config
+- perf: performance improvement
+- revert: revert a previous commit (format: revert: revert "<original message>")
+
+Rules:
+- Scope is optional, specifies the affected area (e.g. auth, api, storage, ui, config)
+- Description: lowercase, no trailing period, in English
+- One commit = one intention, do not mix fix and refactor
+- For breaking changes, add ! after the type and a BREAKING CHANGE: footer
+- Only include a body if there are multiple distinct changes to explain; for a single focused change, output the title only`
+
+export const SIMPLE_INSTRUCTION = `Based on the provided git diff, generate a short and clear one-line commit message (50-72 characters).`