Add the Astra Q4 prompt freeze and preparation note

[LightChainr]

Astra Q4 prompt freeze and preparation note

Prompt-freeze + preparation record for docs/astra/Q4-why-square-site-resists.md (this ticket sends
that file verbatim to an external math model; I have no such channel, so I freeze and prepare only).

Prompt-freeze record

• SHA-256 785d9f42594070045807de2be851c59a8841722e632cc2cdbb3800680142777f; 6972 chars; 122 lines.
• Self-contained: yes. Does not instruct concatenating other question files (siblings Q1–Q3 exist
  but are not referenced); provenance cites repo artifacts, not other prompts.
• do-not-spend list consistent with the ticket's update evidence: the file's A-lattice row (degree 5,
  height 4) is exactly the counterexample that falsifies "degree ≤ 6 AND height ≤ 3".

Independent exact verification (Ziff 2006 A-lattice quintic)

f(p)=p⁵−4p⁴+3p³+2p²−1: degree 5, height (max |coeff|) = 4. Rational-root test f(±1)≠0 ⇒ no linear
factor; Gauss-lemma quadratic×cubic exclusion (and a brute-force machine check) ⇒ irreducible over
ℚ. Confirms the ticket's counterexample.

Explicit

The literal answer to Q4 is absent — no external-model channel available. This note is not an
answer to Q4. No external-model output fabricated.

Full Matching-One repository CI has not been run for this commit.