Fix mvnw: wrong MAVEN_HOME path and unzip overwrites

Fix mvnw: wrong MAVEN_HOME path and unzip overwrites

Two bugs introduced in the initial mvnw script:

1. apache-maven-3.9.6-bin.zip extracts into apache-maven-3.9.6/ (without
   the -bin suffix), but MAVEN_HOME was set to $DISTRIBUTION_ID which
   includes -bin. Fix: strip -bin suffix with ${DISTRIBUTION_ID%-bin}.

2. unzip without -o flag asks interactively when the cache directory
   already contains files from a previous (partial) run. Fix: add -o
   (overwrite silently).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>