Adapt dtcw bats test suite to the v4 environment model (un-skip the v3 tests)

[raifdmueller]

Context

PR #41 skipped 25 tests across 7 bats files because the v4 dtcw wrapper changed the environment model and the tests still encode v3 behaviour. This issue tracks adapting the dtcw bats suite to the v4 model and un-skipping them.

Root cause (v4 behaviour changes)

1. local is a first-class environment — always detected and preferred. So the env list now reads local … (not none / sdk / docker), and Using environment: local.
2. Direct script invocation — v4 no longer forwards to an sdk-/docker-installed docToolchain, so the mock_doctoolchain / mock_docker call counts are 0.
3. ./dtcw tasks succeeds where v3 exited non-zero (nothing installed → now local runs).
4. Local install ships its own JDK — the system-Java version gate (assert_java_version_supported, dtcw:514) is bypassed, so unsupported-Java scenarios no longer error. ⟶ overlaps with v4: make the supported/installed Java version configurable (currently hard-pinned to 17) #42.
5. docker environment not pulled in yet for v4.

Skipped tests to revisit

File	Tests	Category
docker_environment.bats	forward call to docker	env list / forwarding
install_doctoolchain.bats	show java missing · system with supported Java · missing component · unknown component	env list none→local
install_java.bats	install java (linux/x64) before doctoolchain installed	env list none→local
java_environment.bats	use JAVA_HOME · invalid JAVA_HOME · supported Java 17 · unsupported Java 11 · unsupported Java 8 · unsupported Java 20 · local Java before system Java	Java gate bypassed by local JDK (see #42)
local_environment.bats	tasks - forward to local doctoolchain · overrule config with DTC_CONFIG_FILE	direct invocation / mock not called
pristine_environment.bats	no arguments shows usage · tasks uses local environment - shows install docToolchain · sdk tasks shows install SDKMAN!	local-runs / usage output
sdk_installation.bats	don't show how to install SDKMAN! · doctoolchain installed with sdk - java missing · tasks - forward to sdk doctoolchain · using local with sdk environment fails · using docker with sdk environment fails · installing docker has no side effects · using docker with sdk installation	sdk-forwarding / local-first / docker

All are marked with a skip "v4: …" reason in the source, so they are greppable: grep -rn 'skip "v4' test/.

Acceptance criteria

• Each skipped test is either rewritten to assert the intended v4 behaviour, or removed if the scenario no longer exists in v4.
• The intended v4 environment precedence is decided and documented (local vs. explicitly-requested sdk/docker).
• The Java-version gate behaviour under a bundled local JDK is defined (coordinate with v4: make the supported/installed Java version configurable (currently hard-pinned to 17) #42).
• docker environment tests are re-enabled once v4 docker support lands.
• grep -rn 'skip "v4' test/ returns nothing.
• test/bats/bin/bats --filter-tags '!e2e' test is green without skips on ubuntu and macos.

References

• Holding measure: test(dtcw): skip v3-incompatible bats tests pending v4 suite adaptation #41
• Java-version configurability (overlaps the java_environment skips): v4: make the supported/installed Java version configurable (currently hard-pinned to 17) #42