Improve error handling across all scripts

[devin-ai-integration]

Summary

Systematically adds error checking to ~570 unchecked commands across 177 shell scripts that previously failed silently.

Key patterns fixed:

|| return 1 added to unchecked commands in build/install functions:

• cd — ~66 instances; a failed cd causes all subsequent commands to run in the wrong directory
• wget / git clone — ~33 instances; failed downloads proceeded to build broken/missing sources
• make / cmake — ~150 instances; failed builds were silently ignored
• tar / unzip — ~18 instances; failed extractions left partial/missing files
• mv — ~74 instances; failed moves left files in wrong locations

mkdir -p flag added to ~50 mkdir calls to prevent failures on pre-existing directories.

Piped command patterns fixed (silent failures when left side of pipe fails):

# kweb.sh, reminiscence.sh — wget|tar split into:
wget -q <url> || return 1
tar -xf <file> || return 1
rm -f <file>

# kodi-extra.sh — wget|apt-key split into:
wget -qO /tmp/kodi-repo.gpg.key <url> || return 1
apt-key add /tmp/kodi-repo.gpg.key >/dev/null

Dead error variable fixed in openbor.sh:

# Before: error= set but never checked
error="This script is intended for Raspberry Pis only..."
# After: uses RetroPie's error propagation mechanism
md_ret_errors+=("This script is intended for Raspberry Pis only...")
return 1

install-extras.sh fixes:

• git pull origin — unchecked; now exits on failure
• cp, rm — used in && chains that swallowed errors; replaced with explicit if ! cmd; then ... exit 1; fi
• Complex cp ... && rm ... chains — wrapped in { ... || exit 1; } to catch both failures
• Bare exit → exit 0 / exit 1 for explicit exit codes
• VERSION file read without existence check

Link to Devin session: https://app.devin.ai/sessions/a097d510c3ec42ff871f3bbf2d17cc75
Requested by: @Exarkuniv

[devin-ai-integration]

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