Fix installer interactive detection when stdin is redirected

[cashlycash]

Motivation

• Avoid false non-interactive detection when stdin is piped or redirected so prompts still use the controlling terminal when available.
• Make confirm() reliably choose between reading from /dev/tty and stdin to match real interactive shells.

Description

• Replaced the -t 0 check with is_interactive() that attempts to open /dev/tty via a quiet redirection: ( : < /dev/tty ) >/dev/null 2>&1.
• Updated confirm() to call is_interactive() and read from /dev/tty when available, otherwise fall back to reading from stdin, and normalize accepted yes values (y|Y|yes|YES).
• Added simple runtime diagnostic output in main() to print whether the installer detected an interactive session.

Testing

• Ran bash -n install.sh to validate shell syntax, which succeeded.
• Executed a piped-input shell snippet that simulates redirected stdin to verify confirm() falls back to stdin and the new is_interactive() correctly detects when /dev/tty is openable, which succeeded.
• Manually inspected the modified install.sh sections (is_interactive, confirm, and main) to confirm the intended input-selection behavior.

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Codex Task

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Reinstate no-confirm short-circuit in prompt handler

The updated confirm() implementation no longer checks PEAPOD_NO_CONFIRM, so --yes/-y (which still sets that variable in main) no longer skips prompts. This is a behavioral regression for automated installs: install.sh --yes now attempts to read input instead of auto-accepting, and in non-interactive runs it can terminate early on EOF rather than proceeding. Please restore the early return when PEAPOD_NO_CONFIRM=1 before any read call.

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