refactor: apply minimal tfcode branding

- Rename packages/opencode → packages/tfcode (directory only)
- Rename bin/opencode → bin/tfcode (CLI binary)
- Rename .opencode → .tfcode (config directory)
- Update package.json name and bin field
- Update config directory path references (.tfcode)
- Keep internal code references as 'opencode' for easy upstream sync
- Keep @opencode-ai/* workspace package names

This minimal branding approach allows clean merges from upstream
opencode repository while providing tfcode branding for users.

packages/tfcode/src/auth/index.ts

@@ -0,0 +1,115 @@
+import path from "path"
+import { Effect, Layer, Record, Result, Schema, ServiceMap } from "effect"
+import { makeRunPromise } from "@/effect/run-service"
+import { zod } from "@/util/effect-zod"
+import { Global } from "../global"
+import { Filesystem } from "../util/filesystem"
+
+export const OAUTH_DUMMY_KEY = "opencode-oauth-dummy-key"
+
+const file = path.join(Global.Path.data, "auth.json")
+
+const fail = (message: string) => (cause: unknown) => new Auth.AuthError({ message, cause })
+
+export namespace Auth {
+  export class Oauth extends Schema.Class<Oauth>("OAuth")({
+    type: Schema.Literal("oauth"),
+    refresh: Schema.String,
+    access: Schema.String,
+    expires: Schema.Number,
+    accountId: Schema.optional(Schema.String),
+    enterpriseUrl: Schema.optional(Schema.String),
+  }) {}
+
+  export class Api extends Schema.Class<Api>("ApiAuth")({
+    type: Schema.Literal("api"),
+    key: Schema.String,
+  }) {}
+
+  export class WellKnown extends Schema.Class<WellKnown>("WellKnownAuth")({
+    type: Schema.Literal("wellknown"),
+    key: Schema.String,
+    token: Schema.String,
+  }) {}
+
+  const _Info = Schema.Union([Oauth, Api, WellKnown]).annotate({ discriminator: "type", identifier: "Auth" })
+  export const Info = Object.assign(_Info, { zod: zod(_Info) })
+  export type Info = Schema.Schema.Type<typeof _Info>
+
+  export class AuthError extends Schema.TaggedErrorClass<AuthError>()("AuthError", {
+    message: Schema.String,
+    cause: Schema.optional(Schema.Defect),
+  }) {}
+
+  export interface Interface {
+    readonly get: (providerID: string) => Effect.Effect<Info | undefined, AuthError>
+    readonly all: () => Effect.Effect<Record<string, Info>, AuthError>
+    readonly set: (key: string, info: Info) => Effect.Effect<void, AuthError>
+    readonly remove: (key: string) => Effect.Effect<void, AuthError>
+  }
+
+  export class Service extends ServiceMap.Service<Service, Interface>()("@opencode/Auth") {}
+
+  export const layer = Layer.effect(
+    Service,
+    Effect.gen(function* () {
+      const decode = Schema.decodeUnknownOption(Info)
+
+      const all = Effect.fn("Auth.all")(() =>
+        Effect.tryPromise({
+          try: async () => {
+            const data = await Filesystem.readJson<Record<string, unknown>>(file).catch(() => ({}))
+            return Record.filterMap(data, (value) => Result.fromOption(decode(value), () => undefined))
+          },
+          catch: fail("Failed to read auth data"),
+        }),
+      )
+
+      const get = Effect.fn("Auth.get")(function* (providerID: string) {
+        return (yield* all())[providerID]
+      })
+
+      const set = Effect.fn("Auth.set")(function* (key: string, info: Info) {
+        const norm = key.replace(/\/+$/, "")
+        const data = yield* all()
+        if (norm !== key) delete data[key]
+        delete data[norm + "/"]
+        yield* Effect.tryPromise({
+          try: () => Filesystem.writeJson(file, { ...data, [norm]: info }, 0o600),
+          catch: fail("Failed to write auth data"),
+        })
+      })
+
+      const remove = Effect.fn("Auth.remove")(function* (key: string) {
+        const norm = key.replace(/\/+$/, "")
+        const data = yield* all()
+        delete data[key]
+        delete data[norm]
+        yield* Effect.tryPromise({
+          try: () => Filesystem.writeJson(file, data, 0o600),
+          catch: fail("Failed to write auth data"),
+        })
+      })
+
+      return Service.of({ get, all, set, remove })
+    }),
+  )
+
+  const runPromise = makeRunPromise(Service, layer)
+
+  export async function get(providerID: string) {
+    return runPromise((service) => service.get(providerID))
+  }
+
+  export async function all(): Promise<Record<string, Info>> {
+    return runPromise((service) => service.all())
+  }
+
+  export async function set(key: string, info: Info) {
+    return runPromise((service) => service.set(key, info))
+  }
+
+  export async function remove(key: string) {
+    return runPromise((service) => service.remove(key))
+  }
+}