* feat: add install.sh for one-line release install
Add a POSIX install script that detects OS/arch, resolves the latest
release (override with OCR_VERSION), verifies the SHA-256 checksum
fail-closed, and installs the ocr binary to /usr/local/bin (override
with OCR_INSTALL_DIR, sudo fallback when needed).
README now leads with a single curl | sh command and keeps the manual
per-platform downloads in a collapsible section for Windows and offline
use.
* fix: harden install.sh shell robustness
- replace word-split $SHA_CMD invocation with a sha256() wrapper function
- capture github api response and fail explicitly on curl error instead of
masking it through the tag-parsing pipeline under set -eu
* fix: harden install.sh from local ocr review
- trap INT/TERM in addition to EXIT so the temp dir is cleaned on signals
- install binary with install(1) so sudo installs are root-owned in system dirs
- make sha256() self-contained (errors if no checksum tool) and drop the now
redundant up-front guard
* docs(i18n): sync install one-liner to localized READMEs
Apply the same GitHub Release install-section change as README.md to the
zh-CN/ja-JP/ko-KR/ru-RU translations: lead with the curl|sh one-liner plus
OCR_INSTALL_DIR/OCR_VERSION override example, and move the per-platform
manual downloads into a <details> block.
