docs(BEP-1052): compact redundant explanations and docstrings (~20% shorter)

Overall reduction: 2418 → 1939 lines. The spec kept re-explaining
the same invariants across §1/§2/§3 (required-policy, bulk +
partial-success, `config_name` immutability, admin-path ungated
by `user_writable`, empty → null projection). Hoisted each concept
to one definitive spot and replaced repeated restatements with
brief references.

GraphQL schema:
- Trimmed mutation field docstrings (8 mutations): one-line
  summaries instead of 4-5-line blocks that restated the §3 intro.
- Dropped the boilerplate "Per-item error info for X." / "Result
  of X. Partial success." docstrings on the 12 error/payload types
  — one section header now covers all of them.
- Removed per-field docstrings on inputs/filters where the field
  name is self-describing (`index`, `name`, `createdAt`, AND/OR/NOT).

Pseudocode comments:
- Dropped comments that just restated the method signature
  (`# Strict insert. Errors if any row already exists...`).
- Condensed `AppConfigPolicyRow` field block from multi-line inline
  comments to brief trailing comments.
- Simplified `get_user_app_config` / `search_user_app_configs`
  block comments, keeping the non-obvious SQL join pattern.

§1/§2/§5 prose:
- Consolidated the §2 bulk-orchestration + policy-consultation
  paragraphs (were restating §3's intro).
- Merged §5 "Chain order" + "Read (Merge)" numbered lists into
  their one-paragraph equivalents.
- Tightened §4 REST endpoint descriptions.
- Condensed §6 bootstrap flow.

Rename leftovers fixed in passing:
- `AppConfigSourceConnection` was mistakenly defined twice (one of
  them held merged-view `AppConfig` nodes). Split out
  `AppConfigConnection` / `AppConfigEdge` for the merged path and
  updated `myAppConfigs` return type.
- §3 relationship table still referenced the pre-rename
  `DomainV2.appConfigs` / `UserV2.appConfigs` — corrected to
  `appConfigSources`.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jopemachine