fix(cli): restored piped session persistence

- Treated undefined stdin TTY state as redirected input.

- Honored PI_CODING_AGENT_SESSION_DIR with CLI precedence.

Fixes #7378

packages/coding-agent/src/cli/args.ts

@@ -1,7 +1,7 @@
 /**
  * CLI argument parsing and help display
  */
-import { APP_NAME, CONFIG_DIR_NAME, logger } from "@oh-my-pi/pi-utils";
+import { $env, APP_NAME, CONFIG_DIR_NAME, logger } from "@oh-my-pi/pi-utils";
 import chalk from "chalk";
 import { CLI_THINKING_LEVELS, type ConfiguredThinkingLevel, parseCliThinkingLevel } from "../thinking";
 import { BUILTIN_TOOL_NAMES, HIDDEN_TOOL_NAMES, normalizeToolNames } from "../tools/builtin-names";
@@ -145,6 +145,7 @@ export function parseArgs(inputArgs: string[], extensionFlags?: Map<string, { ty
 		fileArgs: [],
 		unknownFlags: new Map(),
 		unrecognizedFlags: [],
+		sessionDir: $env.PI_CODING_AGENT_SESSION_DIR || undefined,
 	};
 
 	// `--` ends option parsing (POSIX end-of-options). Everything after it is

packages/coding-agent/src/main.ts

@@ -188,8 +188,9 @@ function applyAcpDefaultSettingOverrides(targetSettings: Settings = settings): v
 	applyDefaultSettingOverrides(HOST_DEFAULTED_SETTING_PATHS, targetSettings);
 }
 
-async function readPipedInput(): Promise<string | undefined> {
-	if (process.stdin.isTTY !== false) return undefined;
+/** Reads a non-TTY stdin stream as prompt text. */
+export async function readPipedInput(): Promise<string | undefined> {
+	if (process.stdin.isTTY === true) return undefined;
 	// stdin is a pipe: a producer that never writes nor closes would block
 	// startup forever with zero output. Say what we're blocked on after 1s.
 	const notice = setTimeout(() => {