docs(snapshot): compress to scannable form

Rewrite the analysis doc as a scannable problem list. Same findings
(Bugs 4-10, P2-1..P2-8) and same severities; cut everything that isn't
a current problem.

- Add status-table-at-a-glance at the top: 1 row per finding with
  severity, one-line summary, and direct source link.
- Cut Background, Save-path call chain, the two "What I verified is
  correct" sections, "Implications for net-vs-block", the kick-semantics
  quick-reference (redundant with Bug 10), and the cosmetic-drift list.
- Per finding: one code excerpt where it's load-bearing, a 2-3 sentence
  description, impact / mitigation. Removed long context explanations
  and cross-references that read like an audit trail.
- 1038 -> 453 lines (-56%).

All links still pinned to 639196c. No findings dropped beyond Bugs
1-3 which the prior commit already removed.

Author: ValentaTomas