docs(zh-CN): task #11 draft — architecture/indexing-retrieval-kg.md (60-70%) (#1644)

* docs(zh-CN): draft architecture/indexing-retrieval-kg.md (task #11, 60-70%)

Initial 465-LOC draft covering the 4-domain consolidated architecture doc
per blueprint PR #1637 Section 5.1 line 153. Per PM msg=bbd6afc4:
open draft at 60-70% with stable structure, inline contributor blocks
on subsequent commits.

Structure:
- §1 Four-domain boundary + dependency topology (inc. 5 Protocol map)
- §2 Knowledge Base domain (Bryce-Bryce ORM + 3 services + 5 consumer-owned
  Protocols; two cuiwenbo-supplied placeholder subsections for the KB deep
  fields and ingest transaction edge)
- §3 Indexing domain (DocumentIndexManager reconciler + 5 worker types +
  2 ports CollectionIndexingView / IndexingTrigger)
- §4 Retrieval domain (SearchPipeline + GraphSearchContract one-way bridge
  + G10/G3 enforcement)
- §5 Knowledge Graph domain (5 schemas + graphindex/ 11 subpackage engine
  + CollectionRow Protocol + graph_curation infra + one 410-Gone shim)
- §6 Shared infrastructure (aperag/schema/common.py 8 primitives +
  dual-hook Scenario A; cuiwenbo supply slots flagged)
- §7 Three runtime flows (document ingestion / retrieval / KG curation)
- §8 Gate discipline (G1 / G10 / G3 / G14 / G19 + common.py admission +
  indexing HTTP absence)

Cross-ref discipline: all canonical invariants hyperlink to
`docs/modularization/architecture.md` anchors, no duplication. 2 marked
cuiwenbo-contributor placeholders in §2.5 + §6.1 + §6.2 kept visible so
reviewer knows where inline markdown blocks will land next commit.

Per PM msg=06b3fe38: task #11 reassigned huangheng after Bryce unclaim
(msg=1e91fdde / PM msg=baaea640). cuiwenbo remains contributor/reviewer
(msg=7193ad36 + 4 blocks msg=5398971a / msg=...).

* docs(zh-CN): inline cuiwenbo contributor blocks into indexing-retrieval-kg

Inlines compact distilled versions of the 4 markdown blocks cuiwenbo
posted in task #11 thread (msg=f58f4310 / msg=da878ebe / msg=179d4a3e /
msg=5398971a), per PM msg=fd617915 "优先 cross-ref，能不复制就不复制，
避免这篇被 contributor 细节撑得过大":

- §2.5 swapped placeholder → "KB as first consumer-owned Protocol
  landing" focused on the 4 DI slots, the boundary test enforcement
  direction, and the KB/conversation dual-QuotaOps example.
- §2.6 new "Status machines" subsection with the three key enums +
  the lesson 9a-sexdec User write facade cross-ref.
- §6.1 replaced placeholder with concrete "禁止进 common.py" negative
  examples (Collection / ChatMessage / AgentMessage / User ORM) +
  the common.py-vs-aggregate-module discriminator.
- §6.2 replaced placeholder with the two-load-order convergence
  walkthrough; the sys.modules.get rationale is kept, rest cross-
  refs SSoT §3.3.

All retained details stay ≤ the narrow "cross-ref first, inline
strictly where the detail is worth repeating in zh-CN" discipline.

Author: earayu