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/AGENTS.md

@@ -0,0 +1,63 @@
+# opencode database guide
+
+## Database
+
+- **Schema**: Drizzle schema lives in `src/**/*.sql.ts`.
+- **Naming**: tables and columns use snake*case; join columns are `<entity>_id`; indexes are `<table>*<column>\_idx`.
+- **Migrations**: generated by Drizzle Kit using `drizzle.config.ts` (schema: `./src/**/*.sql.ts`, output: `./migration`).
+- **Command**: `bun run db generate --name <slug>`.
+- **Output**: creates `migration/<timestamp>_<slug>/migration.sql` and `snapshot.json`.
+- **Tests**: migration tests should read the per-folder layout (no `_journal.json`).
+
+# opencode Effect rules
+
+Use these rules when writing or migrating Effect code.
+
+See `specs/effect-migration.md` for the compact pattern reference and examples.
+
+## Core
+
+- Use `Effect.gen(function* () { ... })` for composition.
+- Use `Effect.fn("Domain.method")` for named/traced effects and `Effect.fnUntraced` for internal helpers.
+- `Effect.fn` / `Effect.fnUntraced` accept pipeable operators as extra arguments, so avoid unnecessary outer `.pipe()` wrappers.
+- Use `Effect.callback` for callback-based APIs.
+- Prefer `DateTime.nowAsDate` over `new Date(yield* Clock.currentTimeMillis)` when you need a `Date`.
+
+## Schemas and errors
+
+- Use `Schema.Class` for multi-field data.
+- Use branded schemas (`Schema.brand`) for single-value types.
+- Use `Schema.TaggedErrorClass` for typed errors.
+- Use `Schema.Defect` instead of `unknown` for defect-like causes.
+- In `Effect.gen` / `Effect.fn`, prefer `yield* new MyError(...)` over `yield* Effect.fail(new MyError(...))` for direct early-failure branches.
+
+## Runtime vs Instances
+
+- Use the shared runtime for process-wide services with one lifecycle for the whole app.
+- Use `src/effect/instances.ts` for per-directory or per-project services that need `InstanceContext`, per-instance state, or per-instance cleanup.
+- If two open directories should not share one copy of the service, it belongs in `Instances`.
+- Instance-scoped services should read context from `InstanceContext`, not `Instance.*` globals.
+
+## Preferred Effect services
+
+- In effectified services, prefer yielding existing Effect services over dropping down to ad hoc platform APIs.
+- Prefer `FileSystem.FileSystem` instead of raw `fs/promises` for effectful file I/O.
+- Prefer `ChildProcessSpawner.ChildProcessSpawner` with `ChildProcess.make(...)` instead of custom process wrappers.
+- Prefer `HttpClient.HttpClient` instead of raw `fetch`.
+- Prefer `Path.Path`, `Config`, `Clock`, and `DateTime` when those concerns are already inside Effect code.
+- For background loops or scheduled tasks, use `Effect.repeat` or `Effect.schedule` with `Effect.forkScoped` in the layer definition.
+
+## Instance.bind — ALS for native callbacks
+
+`Instance.bind(fn)` captures the current Instance AsyncLocalStorage context and restores it synchronously when called.
+
+Use it for native addon callbacks (`@parcel/watcher`, `node-pty`, native `fs.watch`, etc.) that need to call `Bus.publish`, `Instance.state()`, or anything that reads `Instance.directory`.
+
+You do not need it for `setTimeout`, `Promise.then`, `EventEmitter.on`, or Effect fibers.
+
+```typescript
+const cb = Instance.bind((err, evts) => {
+  Bus.publish(MyEvent, { ... })
+})
+nativeAddon.subscribe(dir, cb)
+```