[DO NOT MERGE] refactor(sdk): unify CRDT codec into a parse-once pipeline

[cyaiox]

Phase 3 of the authoritative-server network refactor — the highest-
risk phase, executed with byte-identical wire goldens (the 7
characterization snapshots pass unmodified):

• network/codec.ts (server/utils.ts renamed, chunking.ts absorbed) is
  the sole owner of read/translate/pack; nothing else in the layer
  parses or packs CRDT bytes
• server ingest walks each inbound buffer exactly once: validation
  consumes the parsed form and broadcast re-packs the retained byte
  slices — the structural re-parse inside the old chunker is gone
  (2 parses → 1 per buffer, asserted by a spy-based test)
• packChunks: one place chunk boundaries are decided, O(1) size
  accounting via currentWriteOffset, lazy pull with copy-before-reuse
  so producers can yield views over a scratch buffer instead of
  allocating 10KB per message
• one oversize error path shared by dumps and broadcasts, always-on,
  naming component, entity, byte size, and the 12KB ceiling (chore: change s3 secrets and comment an installable package to test #8 green)
• state.ts dump path now measures the actual emitted slice instead of
  payload-only bytes (was undercounting headers by ~28B/message)

Red defect test #8 flips to passing; #10, #11, #12, #13 verified still
red. chunkCrdtMessages survives only as the characterization pin's
composition (ponytail marker with removal path).

Claude-Session: https://claude.ai/code/session_01Kzo6zwrn1CA79S4RN1dgsU

🤖 Generated with Claude Code

https://claude.ai/code/session_01Kzo6zwrn1CA79S4RN1dgsU

---

📚 Stack (splits #1505 — merge top-down within each stack)

Network layer (each PR is one self-contained, independently-green commit):

1. test(sdk): characterization baseline for the network layer refactor #1518 test harness — characterization baseline + red defect suite (this stack's root)
2. [DO NOT MERGE] refactor(sdk): network layer foundations — break cycles, single isServer, logging discipline #1519 foundations — cycle break, single isServer, logging discipline
3. [DO NOT MERGE] feat(sdk): hydration FSM — deterministic late-join and reconnect convergence #1520 hydration FSM — late-join/reconnect correctness
4. [DO NOT MERGE] feat(sdk): default-deny server validation, fixed correction path, O(1) entity lookup #1521 validator — default-deny, correction path, entity index
5. [DO NOT MERGE] refactor(sdk): unify CRDT codec into a parse-once pipeline #1522 codec — parse-once pipeline (wire goldens byte-identical)
6. [DO NOT MERGE] feat(sdk): clients target the authoritative server; registry collisions; players dedupe #1523 topology — targeted sends, registry collisions, players dedupe
7. [DO NOT MERGE] refactor(sdk): parameterize network boot, document the host contract #1524 boot + host-conformance doc
8. [DO NOT MERGE] refactor(sdk): ponytail sweep — delete what the refactor no longer needs #1525 simplification sweep (−95 lines)

sdk-commands (independent of the stack above):

• feat(sdk-commands): namespace and durably persist local dev storage per project #1526 world-storage namespacing (pre-existing WIP, carried from the working tree)
• [DO NOT MERGE] fix(sdk-commands): make the local hammurabi dev server reliable #1527 local dev-server reliability (depends on feat(sdk-commands): namespace and durably persist local dev storage per project #1526)

After a parent squash-merges, the child needs git rebase --onto origin/auth-server <old-parent> <child> — ping the session and it gets restacked.

[github-actions]

Test this pull request

• The @dcl/sdk package can be tested in scenes by running

  npm install "https://sdk-team-cdn.decentraland.org/@dcl/js-sdk-toolchain/branch/stack/05-codec/dcl-sdk-7.25.1-31013698504.commit-9437977.tgz"

• The @dcl/js-runtime package can be tested in scenes by running

  npm install "https://sdk-team-cdn.decentraland.org/@dcl/js-sdk-toolchain/branch/stack/05-codec/@dcl/js-runtime/dcl-js-runtime-7.25.1-31013698504.commit-9437977.tgz"

• To test with npx init

  export SDK_COMMANDS="https://sdk-team-cdn.decentraland.org/@dcl/js-sdk-toolchain/branch/stack/05-codec/dcl-sdk-commands-7.25.1-31013698504.commit-9437977.tgz"
  npx $SDK_COMMANDS init

• The /changerealm command to test test in-world

  /changerealm https://sdk-team-cdn.decentraland.org/ipfs/stack/05-codec-e2e
  

• You can preview this build entering:
  https://playground.decentraland.org/?sdk-branch=stack/05-codec