smb: add READ_RAW for ~20× faster file copies

[felixrieseberg]

Win95's redirector was falling back to ~2.8 KB core READs because we advertised no raw mode, so copying a 200 KB file took ~360 round-trips through the emulated ne2k/TCP stack (~10 s). With SMB_COM_READ_RAW it pulls up to 64 KB per round-trip.

Changes

• server.ts — readRaw() handler (response is raw bytes only, no SMB header; 0-byte NetBIOS frame on error/EOF per [MS-CIFS] §2.2.4.24). Negotiate now advertises MaxRawSize=65535 + CAP_RAW_MODE (NT dialect) and RawMode bit 0 (LM dialect). Per-packet hex capture is now gated on WIN95_SMB_CAPTURE instead of always-on.
• smb.ts — CMD_READ_RAW = 0x1a
• test-standalone.ts — READ_RAW happy-path + bad-fid → 0-byte cases

Test

npx tsc --ignoreConfig --module commonjs --target es2020 --esModuleInterop \
  --moduleResolution bundler --types node --outDir /tmp/smb-test --skipLibCheck \
  src/renderer/smb/*.ts && node /tmp/smb-test/test-standalone.js
# 57 passed, 0 failed