sentry-cli (new TS/Bun) chunk-upload code surface

sentry-cli (new TS/Bun) chunk-upload code surface: Entire pipeline in src/lib/api/sourcemaps.ts (~500 lines). Key exports: ChunkServerOptionsSchema (Zod, camelCase), getChunkUploadOptions, uploadArtifactBundle, pickUploadEncoding (prefers zstd>gzip>plain), encodeChunk. Compression: Bun.zstdCompressSync(buf, {level:3}) for zstd, Node zlib gzip L6. Content-Encoding header passes through prepareHeaders() in sentry-client.ts untouched. Build: bun run build → dist-bin/sentry-<platform>. Tests: test/lib/api/sourcemaps.test.ts. All packages must be in devDependencies (CI enforces via bun run check:deps); Bun has native zstd — no new npm dep needed.