Play Framework

fix(launcher): host env beats certs/.env; forward JVM module options (PF-184, PF-183)

Two defects in what a Play JVM is started with. They land together
because the bundle launcher's share of each lives in one script, behind
one warning helper, with one test class.

PF-184. With a variable set both in certs/.env and in the host
environment, play start and play autotest gave the app the host's value
while play run, play test, play precompile and the bundle launcher gave
it the file's. A value passed with `docker run -e` therefore lost to a
certs/.env in the image, the opposite of what the scaffolded
.env.example promises. The bundle also sourced the file, so `pa$$word`
reached the JVM with the shell's pid in it and $(...) was executed.

There is now one rule: a variable the host environment defines, even as
the empty string, is never overridden, and the file is literal KEY=VALUE
text. registerPlayJvmTask sets an entry only when the build's
environment lacks the key. bundle-play.sh reads the file line by line
with loadDotEnv's grammar (split at the first '=', trimmed, one quote
pair removed, last duplicate wins) and never evaluates it. It loads the
file before computing its own defaults, so PLAY_ID and PLAY_PID_FILE
from the file are defaults the host and the --%<id> / --pid-file flags
override; entries are exported only immediately before the exec, so a
key such as IFS or PATH cannot change what the launcher itself does. A
key that is not a variable name, `export FOO=bar` included, is skipped
with a warning that gives the line number and never the value.

PF-183. The bundle launcher forwarded six forms of JVM option and
discarded every other argument without a word, so --add-modules=...,
--enable-preview and -ea never reached the JVM. It now forwards the
module options in their =-joined form, --enable-preview and the
assertion switches, and names each argument it does drop in one line on
stderr, once per invocation including restart. The help text lists what
is forwarded.

Tests: DotEnvPrecedenceTest runs playRun, playStart and playAutotest for
real with the variable in both places, only in the file, and set empty
on the host. BundleLauncherTest covers the launcher's grammar, the
precedence, the literal values, the warnings and the forwarded options,
including a key check that used to fail under a locale whose collation
leaves letters out of A-Z on bash before 5. Verified on a real bundle:
the host value wins, `pa$$word#1 $(touch PWNED)` arrives unchanged with
nothing executed, and --add-modules=jdk.incubator.vector reaches the JVM.

The manual documents certs/.env, its syntax and the precedence rule, and
what the bundle launcher forwards.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>