Add integration test infrastructure and dev container

[c-schuler]

Summary

• Adds Docker-based integration tests that exercise the full VS Code extension + language server pipeline (LSP communication, diagnostics, ELM translation, compiler options validation, multi-file compilation)
• Adds a dev container configuration for developing across both vscode-cql and cql-language-server in a single reproducible environment
• Adds file watcher scripts for automatic rebuilds of both the TypeScript extension and the language server JAR
• Excludes integration tests from the default npm test run so CI unit tests are unaffected

Motivation

Previously there were no end-to-end tests covering the boundary between the extension and the language server. Each repo was tested in isolation with mocked interfaces. This gap allowed issues like compiler options not being applied to go undetected.

Test plan

• docker compose up --build from integration-tests/ passes all 8 tests
• npm test still runs unit tests without regressions (integration tests excluded)
• Dev container opens successfully via Dev Containers: Reopen in Container
• Watch All task rebuilds both projects on source changes
• Rebuild Language Server task produces a working JAR and relinks it

[github-actions]

Coverage after merging feature/integration-tests-dev-container into master will be

69.07%

Coverage Report

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src
extension.api.ts	100%	100%	100%	100%
extension.ts	64.29%	60%	62.50%	64.67%	107–110, 131–133, 139–141, 146–148, 31–38, 41–63, 70–74, 84–91
protocol.ts	100%	100%	100%	100%
statusBar.ts	100%	100%	100%	100%
src/commands
commands.ts	100%	100%	100%	100%
execute-cql.ts	36.24%	100%	45.45%	32.08%	100–105, 108–162, 165–253, 255–277, 323–328, 330–335, 41, 44, 47, 53–99
log-files.ts	70.09%	58.33%	60%	72.22%	24–29, 43–45, 50–53, 60–63, 69–71, 77–79, 84–90
view-elm.ts	94.44%	100%	100%	93.33%	12, 9
src/cql-language-server
cqlLanguageClient.ts	65.58%	87.50%	55.56%	65.15%	100–118, 122, 126–129, 141–146, 165–166, 173–177, 182–198, 37–39, 84, 88–99
languageServerStarter.ts	74.04%	71.43%	80%	73.91%	21–36, 44, 44–45, 71–77
src/cql-service
cqlService.executeCql.ts	73%	100%	66.67%	70.79%	10–34, 9
cqlService.getElm.ts	62.50%	100%	0%	71.43%	6–7
src/java-support
findJavaRuntimes.ts	55.58%	66.67%	78.57%	53.31%	100–104, 107–110, 120, 120–139, 14, 140–149, 15, 150–191, 197–213, 216–243, 251–253, 292–294, 320–322, 324–326, 332–334, 337–341, 346–362, 46–48, 78, 86–99
javaServiceInstaller.ts	94.29%	72.73%	100%	96.57%	124–126, 164–166, 173, 22–24, 60–61
requirements.ts	69.88%	73.68%	66.67%	69.50%	10–11, 115–128, 130–141, 55–68, 72–77
src/log-services
logger.ts	91.94%	75%	100%	93.75%	33–34, 37–39
multi-transport-logger.ts	83.57%	100%	53.33%	86.09%	100, 103–104, 107–108, 111–114, 55–56, 63–64, 95–96, 99
src/model
testCase.ts	95.24%	94.12%	100%	95.35%	82–86
src/utils
file-utils.ts	100%	100%	100%	100%

[brynrhodes]

integration tests work, npm test still works, but I'm getting an error trying to reopen in container (gets an error on trying to add the gid saying it already exists)

[raleigh-g-thompson]

Please rebase on to v0.9.0.