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/effect/instance-context.ts

@@ -0,0 +1,14 @@
+import { ServiceMap } from "effect"
+import type { Project } from "@/project/project"
+
+export declare namespace InstanceContext {
+  export interface Shape {
+    readonly directory: string
+    readonly worktree: string
+    readonly project: Project.Info
+  }
+}
+
+export class InstanceContext extends ServiceMap.Service<InstanceContext, InstanceContext.Shape>()(
+  "opencode/InstanceContext",
+) {}

packages/tfcode/src/effect/instance-registry.ts

@@ -0,0 +1,12 @@
+const disposers = new Set<(directory: string) => Promise<void>>()
+
+export function registerDisposer(disposer: (directory: string) => Promise<void>) {
+  disposers.add(disposer)
+  return () => {
+    disposers.delete(disposer)
+  }
+}
+
+export async function disposeInstance(directory: string) {
+  await Promise.allSettled([...disposers].map((disposer) => disposer(directory)))
+}

packages/tfcode/src/effect/instance-state.ts

@@ -0,0 +1,47 @@
+import { Effect, ScopedCache, Scope } from "effect"
+import { Instance, type Shape } from "@/project/instance"
+import { registerDisposer } from "./instance-registry"
+
+const TypeId = "~opencode/InstanceState"
+
+export interface InstanceState<A, E = never, R = never> {
+  readonly [TypeId]: typeof TypeId
+  readonly cache: ScopedCache.ScopedCache<string, A, E, R>
+}
+
+export namespace InstanceState {
+  export const make = <A, E = never, R = never>(
+    init: (ctx: Shape) => Effect.Effect<A, E, R | Scope.Scope>,
+  ): Effect.Effect<InstanceState<A, E, Exclude<R, Scope.Scope>>, never, R | Scope.Scope> =>
+    Effect.gen(function* () {
+      const cache = yield* ScopedCache.make<string, A, E, R>({
+        capacity: Number.POSITIVE_INFINITY,
+        lookup: () => init(Instance.current),
+      })
+
+      const off = registerDisposer((directory) => Effect.runPromise(ScopedCache.invalidate(cache, directory)))
+      yield* Effect.addFinalizer(() => Effect.sync(off))
+
+      return {
+        [TypeId]: TypeId,
+        cache,
+      }
+    })
+
+  export const get = <A, E, R>(self: InstanceState<A, E, R>) =>
+    Effect.suspend(() => ScopedCache.get(self.cache, Instance.directory))
+
+  export const use = <A, E, R, B>(self: InstanceState<A, E, R>, select: (value: A) => B) =>
+    Effect.map(get(self), select)
+
+  export const useEffect = <A, E, R, B, E2, R2>(
+    self: InstanceState<A, E, R>,
+    select: (value: A) => Effect.Effect<B, E2, R2>,
+  ) => Effect.flatMap(get(self), select)
+
+  export const has = <A, E, R>(self: InstanceState<A, E, R>) =>
+    Effect.suspend(() => ScopedCache.has(self.cache, Instance.directory))
+
+  export const invalidate = <A, E, R>(self: InstanceState<A, E, R>) =>
+    Effect.suspend(() => ScopedCache.invalidate(self.cache, Instance.directory))
+}

packages/tfcode/src/effect/run-service.ts

@@ -0,0 +1,13 @@
+import { Effect, Layer, ManagedRuntime } from "effect"
+import * as ServiceMap from "effect/ServiceMap"
+
+export const memoMap = Layer.makeMemoMapUnsafe()
+
+export function makeRunPromise<I, S, E>(service: ServiceMap.Service<I, S>, layer: Layer.Layer<I, E>) {
+  let rt: ManagedRuntime.ManagedRuntime<I, E> | undefined
+
+  return <A, Err>(fn: (svc: S) => Effect.Effect<A, Err, I>, options?: Effect.RunOptions) => {
+    rt ??= ManagedRuntime.make(layer, { memoMap })
+    return rt.runPromise(service.use(fn), options)
+  }
+}