[Feature]: Sync facade + DIRAC migration adapter spike

[aldbr]

User Story

As a DIRAC maintainer during the transition,
I want a synchronous facade over the async interCEde contract and a documented mapping from the
DIRAC CE conventions,
So that DIRAC's SiteDirector/PushJobAgent/RemoteRunner can adopt interCEde backends before the
DiracX tasks exist, without a hand-maintained parallel sync API.

Feature Description

• Sync facade (interCEde, Tier B): run-to-completion wrapper over the async protocols, usable
  only outside an event loop; generated/thin, never a second hand-written contract (IC-ADR-001
  Open Issues). Decide its lifetime (transition-only vs kept).
• Migration mapping doc (interCEde docs; adapter code belongs in DIRAC): the translation
  table from the effective DIRAC contract to interCEde —
  "<ref>:::<stamp>" ↔ JobHandle; PilotStampDict ↔ Submission.handles; S_OK/S_ERROR +
  load-bearing keys (Value, CEInfoDict, PilotStampDict, ExecutableToKeep) ↔ typed
  results/exceptions; available() slot math ↔ caller policy over LoadReporter.counts() +
  CS MaxTotalJobs/MaxWaitingJobs; Tag: Token ↔ IC-ADR-003 credential config; CS
  ParametersDict keys ↔ typed backend config (registry request).
• Spike: a dirac-admin-debug-ce-equivalent script driving an interCEde backend through the
  facade (submit → status → fetch → kill) — the smallest end-to-end proof a DIRAC-side adapter is
  writable.

Definition of Done

• Sync facade shipped + tested (asserts refusal inside a running loop)
• Mapping doc covers every load-bearing DIRAC convention found in the consumer analysis
• Debug-CLI spike drives a real backend (Slurm stack) through the facade in CI
• Facade lifetime decision recorded

Alternatives Considered

• Parallel hand-written sync protocol — re-creates the two-surface drift the ADR indicts; rejected.
• Putting the S_OK/S_ERROR adapter inside interCEde — DIRAC vocabulary doesn't belong in a
  WMS-agnostic library; only the facade (sync-over-async) is interCEde's.

Additional Context

Deferred consumers to keep in mind while writing the mapping: PushJobAgent
(outputs=["/"] → OutputSpec "everything"), RemoteRunner (same lifecycle), WMSUtilities
(killPilotsInQueues bulk kill).