docs(index-engine): fold graph operational burden into §8

[samkeen]

Restructure §8 into engine risks vs. operational burden, capturing the
standing costs of an id-keyed graph under [[path|title]] links: move-time
write amplification, out-of-band move repair limits, the permanent
derived-index invariants, and the suggestion-lifecycle review cost.

Co-Authored-By: Claude Opus 4.8 noreply@anthropic.com
Claude-Session: https://claude.ai/code/session_01JB6NH825tvoJU6mKdBs67f

Summary by CodeRabbit

• Documentation
  • Expanded the risks section with additional operational considerations and open questions.
  • Added guidance on tradeoffs such as link update overhead, move handling limitations, maintaining index consistency during edits, and managing suggestion lifecycle and provenance invalidation.

[coderabbitai]

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Free

Run ID: cbac70e0-40fe-4a7e-b21a-a1065920b2d8

📥 Commits

Reviewing files that changed from the base of the PR and between 25361c7 and 2669fb6.

📒 Files selected for processing (1)

• index-engine.md

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📝 Walkthrough

Walkthrough

Section 8 of index-engine.md is renamed to "Risks, open questions & operational burden" with an added "Engine risks & open questions" subheading. A new subsection details operational tradeoffs: move/link-write amplification, out-of-band move degradation, derived-index invariant preservation, and suggestion lifecycle/provenance invalidation.

Changes

Index Engine Docs

Layer / File(s)	Summary
Section 8 expansion and operational burden content index-engine.md	Section 8 heading broadened to include operational burden; new subheading added for engine risks; new subsection added covering move/link rewrite amplification, dangling link handling, derived-index invariants, and review-layer suggestion/provenance implications.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

A rabbit hopped through the vault one day,
Found links and moves in grand array.
"Operational burden," she wrote with care,
Invariants and amplification laid bare.
Now the doc is complete — hip hip hooray! 🐇

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