adds pre-release support

[raleigh-g-thompson]

closes #148

Problem

The extension had no way to track SNAPSHOT language server builds during active development. javaServiceInstaller.ts only knew how to download from Maven Central, which only hosts release artifacts. SNAPSHOT JARs live on the Sonatype Central snapshots repo and require resolving maven-metadata.xml to find the actual timestamped filename. The extension version was also stored with a -SNAPSHOT suffix, which vsce rejects as invalid semver.

Changes

javaServiceInstaller.ts — SNAPSHOT resolution

• Adds resolveSnapshotUrl(), which fetches maven-metadata.xml from the Sonatype snapshots repo and extracts the timestamped artifact value to construct the final JAR URL.
• getSearchUrl() is now async and branches on whether the version ends with -SNAPSHOT. SNAPSHOT JARs are never cached — installServiceIfMissing always re-downloads when a SNAPSHOT version is configured so the extension picks up the latest build on each activation. Release versions continue to resolve from Maven Central unchanged.
• package.json — version + publish scripts
• Strips -SNAPSHOT from the extension version since vsce requires valid semver. Adds publish and publish:prerelease npm scripts as convenience wrappers around vsce publish and vsce publish --pre-release.
• README.md — updated versioning docs
• Replaces the odd/even minor version scheme (which the team doesn't use) with docs for the --pre-release flag approach. - Covers both the pre-release and stable release processes.

No LS-side changes required. SNAPSHOT JARs are already published by the existing mvn deploy step in the LS CI.

[github-actions]

Coverage after merging feature/prerelease-publishing into master will be

66.13%

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	27.08%	100%	20%	26.67%	22–48, 50–53, 55–82, 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	83.20%	70.83%	93.33%	83.89%	100, 160–162, 200–202, 209, 22–24, 60–61, 70–95, 98–99
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	85.25%	71.43%	83.33%	87.50%	20–22, 33–34, 37–39
multi-transport-logger.ts	81.29%	100%	46.67%	84.35%	100, 103–104, 107–108, 111–114, 55–56, 59–60, 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%