Changed PACKAGE_NAME from 'oh-my-openagent' to 'oh-my-opencode' in
auto-update-checker/constants.ts to match package.json. This fixes
getCachedVersion() returning null, causing 'unknown' in version toast.
TDD: red-green confirmed. 39 tests pass, tsc clean.
Closes#3129
Fixes#1920
Installer-written exact versions (e.g., oh-my-opencode@3.5.2) were incorrectly treated as user-pinned, blocking auto-updates for all installer users.
Fix isPinned to only block auto-update when pinnedVersion is an explicit semver string (user's intent). Channel tags (latest, beta, next) and bare package name all allow auto-update.
Fix installer fallback to return bare PACKAGE_NAME for stable versions and PACKAGE_NAME@{channel} for prerelease versions, preserving channel tracking.
YeonGyu-Kim