Harden local services and make setup portable

[btjones-me]

A fresh checkout currently depends on personal Java paths and a deployment-specific Google project, and its local relay/legacy recorder trust every loopback caller. This makes onboarding fragile and lets unrelated local callers consume model credit or interfere with recordings.

This change provides a documented local setup and shared security boundaries while retaining the existing 1.16.5 gameplay routes.

Changes

• Resolve Java through MC_JAVA_HOME/JAVA_HOME/PATH and ffmpeg through configuration; add verified server setup, shared Java builds, a doctor command, and SETUP.md. Preserve existing server configuration/worlds and leave EULA acceptance explicit.
• Centralize explicit key-file, project-specific environment, or configurable Google Secret Manager credentials. Remove the original Google project and inspector-injected relay/transport patches.
• Authenticate the loopback relay, validate Host/Origin/content type/model/output limits, cap concurrency and total request attempts, reject redirects, and remove automatic retries/hedged paid calls. Provider-side monetary limits remain necessary.
• Authenticate and bound legacy recording uploads, enforce capture lifecycle/quota checks, reject malformed URLs, and abort failed browser recordings without falsely marking them complete. Bind the legacy browser viewer to loopback.
• Pin direct npm versions, make dependency patching explicit rather than a postinstall hook, and override uuid to 11.1.1 for GHSA-w5hq-g745-h8pq. Pin SHA-256 digests for executable Maven overrides and verify caches before reuse.
• Replace legacy Log4j 2.8.1 with pinned 2.26.1 for the renderer and server launch classpath.
• Add Linux tests/macOS Java-build CI. Restrict automatic test discovery to unit tests so historical world-mutating setup scripts are not accidentally executed. Repair a stale terrain mock in the existing navigation test.

Validation

• Clean npm ci --ignore-scripts followed by npm run prepare:local.
• npm test: 115 passed.
• npm run test:setup: 12 Node security/lifecycle tests + 4 Python setup tests passed. Includes unauthorized/cross-origin/rebound-Host requests with zero upstream calls, oversized chunked bodies, concurrency/call limits, legitimate authenticated relay behavior, upload quotas/replay rejection, and recorder failure cleanup.
• npm audit --omit=dev: 0 reported vulnerabilities at validation time.
• Observer and native-view Java agents compile successfully with Java 21 targeting Java 17.
• Verified native dependencies (--libraries-only), downloaded/verified server, and launched the server with updated Log4j and observer. It reached the expected unaccepted-EULA exit without creating a world.
• GitHub Actions on the fork: Linux unit/setup tests and observer build, plus macOS native dependency installation and both Java builds, passed.
• Python/JavaScript syntax checks and git diff --check passed.
• Independent read-only bypass/regression review; both reported recorder failure cases were fixed and covered by tests.

Compatibility and limits

Existing users must explicitly configure credentials and run the new setup steps. Native rendering remains macOS-only; Intel library selection is implemented but has not been live-tested. The pre-EULA server bootstrap emits legacy Mojang Log4j plugin-registration warnings. No paid model requests, EULA acceptance, complete gameplay run, or native video-rendering run was performed. A live isolated gameplay/recording check remains necessary before treating the setup as fully validated. This is hardening, not an OS sandbox or a general-purpose arbitrary-world agent.