chore(C-373): purge deferred vapor docs — truthful hallway

[kaizencycle]

C-373: Deferred Vapor Purge (queued from PR #21)

Handoff: ATLAS HANDOFF C-373 — "truthful front door, truthful hallway"

PR #21 explicitly deferred these files. This PR clears the hallway.

Changes

File	Action
QUICK_START.md	Stub → README Quick Start
SETUP.md	Stub → README + CONTRIBUTING
docs/PRODUCT_SPEC.md	Truth-only scope doc
docs/getting-started/README.md	Stub → README + canon links

Intent

epicon_id: EPICON_C-373_DOCS_deferred-vapor-purge_v1
ledger_id: mobius:epicon:mvp-extraction-c373
scope: docs
mode: normal
issued_at: 2026-07-15T00:00:00Z
expires_at: 2026-08-15T00:00:00Z
justification:
  VALUES INVOKED: integrity, transparency
  REASONING: README is truth-only; secondary docs still served vapor two clicks deep.
  ANCHORS: PR #21 deferral list; README evidence-first standard
  BOUNDARIES: Docs only
  COUNTERFACTUAL: If stub removes needed info, expand CONTRIBUTING not vapor
counterfactuals:
  - If contributors lose setup guidance, expand CONTRIBUTING