chore(oss): audit the server package and resync the SDK mirrors

Split the 657-line operation service into eor, submit, and verify
modules, add the AGENT_REVOKED and KEY_RETIRED codes the Backend already
emits, and condense every multi-line comment. Mirror Node, Python, and
Go at 2.1.0 with the deep-health 503, non-idempotent retry, rotation
grace, and path-encoding fixes. Document which routes and response
fields the self-hosted server does not provide.

Claude-Session: https://claude.ai/code/session_01Agoc9bRVE9KL7mmWtey9Vq

packages/server/src/shared/constants/errors.ts

@@ -5,7 +5,9 @@ export const ERROR_CODES: Readonly<Record<ErrorCode, string>> = {
   INVALID_SIGNATURE: 'The operation signature is invalid.',
   UNKNOWN_AGENT: 'The specified agent does not exist.',
   KEY_REVOKED: 'The signing key has been revoked.',
+  KEY_RETIRED: 'The signing key has been retired.',
   AGENT_FROZEN: 'The agent is frozen and cannot submit operations.',
+  AGENT_REVOKED: 'The agent has been revoked.',
   TTL_EXPIRED: 'The operation TTL has expired.',
   REPLAY_DETECTED: 'A duplicate nonce was detected (replay attack).',
   PREV_HASH_MISMATCH: 'The previous chain hash does not match.',