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/flag/flag.ts

@@ -0,0 +1,128 @@
+import { Config } from "effect"
+
+function truthy(key: string) {
+  const value = process.env[key]?.toLowerCase()
+  return value === "true" || value === "1"
+}
+
+function falsy(key: string) {
+  const value = process.env[key]?.toLowerCase()
+  return value === "false" || value === "0"
+}
+
+export namespace Flag {
+  export const OPENCODE_AUTO_SHARE = truthy("OPENCODE_AUTO_SHARE")
+  export const OPENCODE_GIT_BASH_PATH = process.env["OPENCODE_GIT_BASH_PATH"]
+  export const OPENCODE_CONFIG = process.env["OPENCODE_CONFIG"]
+  export declare const OPENCODE_TUI_CONFIG: string | undefined
+  export declare const OPENCODE_CONFIG_DIR: string | undefined
+  export const OPENCODE_CONFIG_CONTENT = process.env["OPENCODE_CONFIG_CONTENT"]
+  export const OPENCODE_DISABLE_AUTOUPDATE = truthy("OPENCODE_DISABLE_AUTOUPDATE")
+  export const OPENCODE_ALWAYS_NOTIFY_UPDATE = truthy("OPENCODE_ALWAYS_NOTIFY_UPDATE")
+  export const OPENCODE_DISABLE_PRUNE = truthy("OPENCODE_DISABLE_PRUNE")
+  export const OPENCODE_DISABLE_TERMINAL_TITLE = truthy("OPENCODE_DISABLE_TERMINAL_TITLE")
+  export const OPENCODE_PERMISSION = process.env["OPENCODE_PERMISSION"]
+  export const OPENCODE_DISABLE_DEFAULT_PLUGINS = truthy("OPENCODE_DISABLE_DEFAULT_PLUGINS")
+  export const OPENCODE_DISABLE_LSP_DOWNLOAD = truthy("OPENCODE_DISABLE_LSP_DOWNLOAD")
+  export const OPENCODE_ENABLE_EXPERIMENTAL_MODELS = truthy("OPENCODE_ENABLE_EXPERIMENTAL_MODELS")
+  export const OPENCODE_DISABLE_AUTOCOMPACT = truthy("OPENCODE_DISABLE_AUTOCOMPACT")
+  export const OPENCODE_DISABLE_MODELS_FETCH = truthy("OPENCODE_DISABLE_MODELS_FETCH")
+  export const OPENCODE_DISABLE_CLAUDE_CODE = truthy("OPENCODE_DISABLE_CLAUDE_CODE")
+  export const OPENCODE_DISABLE_CLAUDE_CODE_PROMPT =
+    OPENCODE_DISABLE_CLAUDE_CODE || truthy("OPENCODE_DISABLE_CLAUDE_CODE_PROMPT")
+  export const OPENCODE_DISABLE_CLAUDE_CODE_SKILLS =
+    OPENCODE_DISABLE_CLAUDE_CODE || truthy("OPENCODE_DISABLE_CLAUDE_CODE_SKILLS")
+  export const OPENCODE_DISABLE_EXTERNAL_SKILLS =
+    OPENCODE_DISABLE_CLAUDE_CODE_SKILLS || truthy("OPENCODE_DISABLE_EXTERNAL_SKILLS")
+  export declare const OPENCODE_DISABLE_PROJECT_CONFIG: boolean
+  export const OPENCODE_FAKE_VCS = process.env["OPENCODE_FAKE_VCS"]
+  export declare const OPENCODE_CLIENT: string
+  export const OPENCODE_SERVER_PASSWORD = process.env["OPENCODE_SERVER_PASSWORD"]
+  export const OPENCODE_SERVER_USERNAME = process.env["OPENCODE_SERVER_USERNAME"]
+  export const OPENCODE_ENABLE_QUESTION_TOOL = truthy("OPENCODE_ENABLE_QUESTION_TOOL")
+
+  // Experimental
+  export const OPENCODE_EXPERIMENTAL = truthy("OPENCODE_EXPERIMENTAL")
+  export const OPENCODE_EXPERIMENTAL_FILEWATCHER = Config.boolean("OPENCODE_EXPERIMENTAL_FILEWATCHER").pipe(
+    Config.withDefault(false),
+  )
+  export const OPENCODE_EXPERIMENTAL_DISABLE_FILEWATCHER = Config.boolean(
+    "OPENCODE_EXPERIMENTAL_DISABLE_FILEWATCHER",
+  ).pipe(Config.withDefault(false))
+  export const OPENCODE_EXPERIMENTAL_ICON_DISCOVERY =
+    OPENCODE_EXPERIMENTAL || truthy("OPENCODE_EXPERIMENTAL_ICON_DISCOVERY")
+
+  const copy = process.env["OPENCODE_EXPERIMENTAL_DISABLE_COPY_ON_SELECT"]
+  export const OPENCODE_EXPERIMENTAL_DISABLE_COPY_ON_SELECT =
+    copy === undefined ? process.platform === "win32" : truthy("OPENCODE_EXPERIMENTAL_DISABLE_COPY_ON_SELECT")
+  export const OPENCODE_ENABLE_EXA =
+    truthy("OPENCODE_ENABLE_EXA") || OPENCODE_EXPERIMENTAL || truthy("OPENCODE_EXPERIMENTAL_EXA")
+  export const OPENCODE_EXPERIMENTAL_BASH_DEFAULT_TIMEOUT_MS = number("OPENCODE_EXPERIMENTAL_BASH_DEFAULT_TIMEOUT_MS")
+  export const OPENCODE_EXPERIMENTAL_OUTPUT_TOKEN_MAX = number("OPENCODE_EXPERIMENTAL_OUTPUT_TOKEN_MAX")
+  export const OPENCODE_EXPERIMENTAL_OXFMT = OPENCODE_EXPERIMENTAL || truthy("OPENCODE_EXPERIMENTAL_OXFMT")
+  export const OPENCODE_EXPERIMENTAL_LSP_TY = truthy("OPENCODE_EXPERIMENTAL_LSP_TY")
+  export const OPENCODE_EXPERIMENTAL_LSP_TOOL = OPENCODE_EXPERIMENTAL || truthy("OPENCODE_EXPERIMENTAL_LSP_TOOL")
+  export const OPENCODE_DISABLE_FILETIME_CHECK = Config.boolean("OPENCODE_DISABLE_FILETIME_CHECK").pipe(
+    Config.withDefault(false),
+  )
+  export const OPENCODE_EXPERIMENTAL_PLAN_MODE = OPENCODE_EXPERIMENTAL || truthy("OPENCODE_EXPERIMENTAL_PLAN_MODE")
+  export const OPENCODE_EXPERIMENTAL_WORKSPACES = OPENCODE_EXPERIMENTAL || truthy("OPENCODE_EXPERIMENTAL_WORKSPACES")
+  export const OPENCODE_EXPERIMENTAL_MARKDOWN = !falsy("OPENCODE_EXPERIMENTAL_MARKDOWN")
+  export const OPENCODE_MODELS_URL = process.env["OPENCODE_MODELS_URL"]
+  export const OPENCODE_MODELS_PATH = process.env["OPENCODE_MODELS_PATH"]
+  export const OPENCODE_DB = process.env["OPENCODE_DB"]
+  export const OPENCODE_DISABLE_CHANNEL_DB = truthy("OPENCODE_DISABLE_CHANNEL_DB")
+  export const OPENCODE_SKIP_MIGRATIONS = truthy("OPENCODE_SKIP_MIGRATIONS")
+  export const OPENCODE_STRICT_CONFIG_DEPS = truthy("OPENCODE_STRICT_CONFIG_DEPS")
+
+  function number(key: string) {
+    const value = process.env[key]
+    if (!value) return undefined
+    const parsed = Number(value)
+    return Number.isInteger(parsed) && parsed > 0 ? parsed : undefined
+  }
+}
+
+// Dynamic getter for OPENCODE_DISABLE_PROJECT_CONFIG
+// This must be evaluated at access time, not module load time,
+// because external tooling may set this env var at runtime
+Object.defineProperty(Flag, "OPENCODE_DISABLE_PROJECT_CONFIG", {
+  get() {
+    return truthy("OPENCODE_DISABLE_PROJECT_CONFIG")
+  },
+  enumerable: true,
+  configurable: false,
+})
+
+// Dynamic getter for OPENCODE_TUI_CONFIG
+// This must be evaluated at access time, not module load time,
+// because tests and external tooling may set this env var at runtime
+Object.defineProperty(Flag, "OPENCODE_TUI_CONFIG", {
+  get() {
+    return process.env["OPENCODE_TUI_CONFIG"]
+  },
+  enumerable: true,
+  configurable: false,
+})
+
+// Dynamic getter for OPENCODE_CONFIG_DIR
+// This must be evaluated at access time, not module load time,
+// because external tooling may set this env var at runtime
+Object.defineProperty(Flag, "OPENCODE_CONFIG_DIR", {
+  get() {
+    return process.env["OPENCODE_CONFIG_DIR"]
+  },
+  enumerable: true,
+  configurable: false,
+})
+
+// Dynamic getter for OPENCODE_CLIENT
+// This must be evaluated at access time, not module load time,
+// because some commands override the client at runtime
+Object.defineProperty(Flag, "OPENCODE_CLIENT", {
+  get() {
+    return process.env["OPENCODE_CLIENT"] ?? "cli"
+  },
+  enumerable: true,
+  configurable: false,
+})