fix(server): respect configured OpenCode auth (#366)

Fixes #315

## Summary
- stop overwriting configured `OPENCODE_SERVER_USERNAME` and
`OPENCODE_SERVER_PASSWORD` when CodeNomad launches managed OpenCode
servers
- reuse user-provided OpenCode auth from workspace environment or
process env before falling back to generated credentials
- add focused tests for configured, inherited, and generated auth paths

## Testing
- `npx tsx --test
"packages/server/src/workspaces/opencode-auth.test.ts"`
- `npx tsc --noEmit --target ES2020 --module ESNext --moduleResolution
Node --strict --esModuleInterop --types node
"packages/server/src/workspaces/opencode-auth.ts"
"packages/server/src/workspaces/opencode-auth.test.ts"`
- `git diff --check`

## Notes
- full server workspace typecheck still has unrelated baseline failures
in this branch (`commander` typings and missing `fuzzysort` types)

packages/server/src/workspaces/manager.ts

@@ -13,10 +13,9 @@ import { Logger } from "../logger"
 import { getOpencodeConfigDir } from "../opencode-config.js"
 import {
   buildOpencodeBasicAuthHeader,
-  DEFAULT_OPENCODE_USERNAME,
-  generateOpencodeServerPassword,
   OPENCODE_SERVER_PASSWORD_ENV,
   OPENCODE_SERVER_USERNAME_ENV,
+  resolveOpencodeServerAuth,
 } from "./opencode-auth"
 
 const STARTUP_STABILITY_DELAY_MS = 1500
@@ -124,8 +123,10 @@ export class WorkspaceManager {
     const envVars = (serverConfig as any)?.environmentVariables
     const userEnvironment = envVars && typeof envVars === "object" && !Array.isArray(envVars) ? (envVars as any) : {}
 
-    const opencodeUsername = DEFAULT_OPENCODE_USERNAME
-    const opencodePassword = generateOpencodeServerPassword()
+    const { username: opencodeUsername, password: opencodePassword } = resolveOpencodeServerAuth({
+      userEnvironment,
+      processEnv: process.env,
+    })
     const authorization = buildOpencodeBasicAuthHeader({ username: opencodeUsername, password: opencodePassword })
     if (!authorization) {
       throw new Error("Failed to build OpenCode auth header")

packages/server/src/workspaces/opencode-auth.test.ts

@@ -0,0 +1,41 @@
+import assert from "node:assert/strict"
+import { describe, it } from "node:test"
+
+import { resolveOpencodeServerAuth } from "./opencode-auth"
+
+describe("resolveOpencodeServerAuth", () => {
+  it("uses configured OpenCode auth from workspace environment", () => {
+    const auth = resolveOpencodeServerAuth({
+      userEnvironment: {
+        OPENCODE_SERVER_USERNAME: "alice",
+        OPENCODE_SERVER_PASSWORD: "secret",
+      },
+      processEnv: {},
+      generatePassword: () => "generated",
+    })
+
+    assert.deepEqual(auth, { username: "alice", password: "secret" })
+  })
+
+  it("uses process environment when workspace environment does not provide credentials", () => {
+    const auth = resolveOpencodeServerAuth({
+      userEnvironment: {},
+      processEnv: {
+        OPENCODE_SERVER_PASSWORD: "process-secret",
+      },
+      generatePassword: () => "generated",
+    })
+
+    assert.deepEqual(auth, { username: "codenomad", password: "process-secret" })
+  })
+
+  it("falls back to generated credentials", () => {
+    const auth = resolveOpencodeServerAuth({
+      userEnvironment: {},
+      processEnv: {},
+      generatePassword: () => "generated",
+    })
+
+    assert.deepEqual(auth, { username: "codenomad", password: "generated" })
+  })
+})

packages/server/src/workspaces/opencode-auth.ts

@@ -9,6 +9,32 @@ export function generateOpencodeServerPassword(): string {
   return crypto.randomBytes(32).toString("base64url")
 }
 
+function readConfiguredValue(key: string, ...sources: Array<Record<string, unknown> | undefined>): string | undefined {
+  for (const source of sources) {
+    const value = source?.[key]
+    if (typeof value === "string" && value.trim().length > 0) {
+      return value
+    }
+  }
+  return undefined
+}
+
+export function resolveOpencodeServerAuth(options: {
+  userEnvironment?: Record<string, unknown>
+  processEnv?: NodeJS.ProcessEnv
+  generatePassword?: () => string
+} = {}): { username: string; password: string } {
+  const generatePassword = options.generatePassword ?? generateOpencodeServerPassword
+  const username =
+    readConfiguredValue(OPENCODE_SERVER_USERNAME_ENV, options.userEnvironment, options.processEnv) ??
+    DEFAULT_OPENCODE_USERNAME
+  const password =
+    readConfiguredValue(OPENCODE_SERVER_PASSWORD_ENV, options.userEnvironment, options.processEnv) ??
+    generatePassword()
+
+  return { username, password }
+}
+
 export function buildOpencodeBasicAuthHeader(params: { username?: string; password?: string }): string | undefined {
   const username = params.username
   const password = params.password