feat(contract): export wire contract from backend and generate frontend types

Adds a zero-dependency `frontend-contract` bin that serializes the real
NoticeStatus variants and FrontendEvent payloads, scripts/gen-contract.mjs
which emits the committed src/services/contract.ts, and a CI job that
regenerates it and fails on a non-empty diff. events.ts now derives its
event map from the generated contract instead of hand-typed shapes.

scripts/gen-contract.mjs

@@ -0,0 +1,91 @@
+import { execFileSync } from 'node:child_process'
+import fs from 'node:fs'
+import path from 'node:path'
+
+/**
+ * Regenerates src/services/contract.ts from the backend wire contract.
+ * Source of truth: `cargo run -p clash-verge --bin frontend-contract` inside
+ * src-tauri, which serializes the same enum variants and event payloads the
+ * app emits at runtime. CI reruns this and fails on a non-empty diff.
+ */
+
+const ROOT = path.resolve(import.meta.dirname, '..')
+const OUT = path.join(ROOT, 'src/services/contract.ts')
+
+const contract = JSON.parse(
+  execFileSync(
+    'cargo',
+    ['run', '-p', 'clash-verge', '--bin', 'frontend-contract', '-q'],
+    {
+      cwd: path.join(ROOT, 'src-tauri'),
+      encoding: 'utf8',
+      maxBuffer: 16 * 1024 * 1024,
+    },
+  ),
+)
+
+if (contract.version !== 1) {
+  throw new Error(`unsupported wire contract version: ${contract.version}`)
+}
+
+/** TS type per event, derived from the serialized sample payload's JSON shape. */
+const payloadType = (name, sample) => {
+  if (sample === null) return 'null'
+  if (typeof sample === 'string') return 'string'
+  if (Array.isArray(sample)) {
+    if (name === 'verge://notice-message') return '[NoticeStatus, string]'
+    throw new Error(`unexpected array payload for ${name}`)
+  }
+  if (typeof sample === 'object') {
+    const keys = Object.keys(sample)
+    if (keys.length === 1 && keys[0] === 'uid') return '{ uid: string }'
+    if (name === 'verge://run-state-changed') return 'RunState'
+    throw new Error(`unexpected object payload for ${name}: ${keys.join(',')}`)
+  }
+  throw new Error(`unexpected payload for ${name}`)
+}
+
+const needsRunState = contract.events.some(
+  (e) => e.name === 'verge://run-state-changed',
+)
+if (!needsRunState)
+  throw new Error('run-state-changed event missing from contract')
+
+const lines = []
+lines.push(
+  '// @generated by scripts/gen-contract.mjs from the backend wire contract. DO NOT EDIT.',
+)
+lines.push('// Regen: pnpm gen:contract')
+lines.push('')
+lines.push("import type { RunState } from './cmds'")
+lines.push('')
+lines.push(
+  '/** Wire status strings from NoticeStatus; keep in sync via `pnpm gen:contract`. */',
+)
+lines.push('export type NoticeStatus =')
+for (const status of contract.noticeStatuses) {
+  lines.push(`  | ${JSON.stringify(status)}`)
+}
+lines.push('')
+lines.push('/** Event name → payload type for every backend-emitted event. */')
+lines.push('export interface VergeEventPayloads {')
+for (const event of contract.events) {
+  const key = JSON.stringify(event.name)
+  lines.push(`  ${key}: ${payloadType(event.name, event.sample)}`)
+}
+lines.push('}')
+lines.push('')
+
+const content = `${lines.join('\n')}\n`
+fs.writeFileSync(OUT, content)
+
+// Match the repo's biome style so CI parity (`git diff --exit-code`) is stable.
+execFileSync(
+  process.platform === 'win32' ? 'pnpm.cmd' : 'pnpm',
+  ['exec', 'biome', 'format', '--write', path.relative(ROOT, OUT)],
+  { cwd: ROOT, stdio: 'ignore' },
+)
+
+console.log(
+  `[gen-contract] wrote ${path.relative(ROOT, OUT)}: ${contract.events.length} events, ${contract.noticeStatuses.length} statuses`,
+)