fix(pkg): retire Nix-mirror per Guix-primary ruling (standards#101)

[hyperpolymath]

Refs standards#101 standards#102. Refs not Closes — this PR does not close any issue.

What

Retire the Nix-mirror in hypatia. Guix-primary + sealed-container-escape is the canonical packaging policy per standards#101; the Nix-mirror was a hand-mirrored twin retired estate-wide.

Verified pure mirror (the standards#102 gate)

guix.scm covers the entire flake devShell dep set verbatim:

flake devShell buildInput	guix.scm native-input
elixir	elixir
erlang	erlang
rustc + cargo + clippy + rustfmt	rust + rust-cargo
idris2	idris2
zig	zig
pkg-config	pkg-config
openssl	openssl

Every flake dep is mirrored — pure mirror per the campaign gate (flake vs Guix ∪ sealed-container). guix.scm's (source #f) is the standard dev-shell form (paired with a real native-inputs list); not the disqualifying empty-stub form. guix shell -D -f guix.scm is the direct replacement for nix develop.

Changes

• git rm flake.nix flake.lock
• CONTRIBUTING.md §Getting Started: nix develop → guix shell -D -f guix.scm (links standards#101).
• TESTING-AUDIT.md Reproducibility row: dereferences flake.nix (canonical = guix.scm).
• Historical audit reports (docs/reports/audit/, docs/governance/CRG-AUDIT-2026-04-18.adoc) retain their flake.nix references as dated snapshots — not edited.

Campaign context

Estate-wide verification (Waves 1–14, ~280 in-scope repos) found that hypatia is the single genuine pure-mirror in the campaign so far. Most other repos have scaffold-stub guix.scm (KEEP+FLAG) or load-bearing flake-only dev tooling (KEEP+DEP). Personally re-verified against the agent-flagged candidates (proof-of-work and tma-mark2 were over-called; hypatia stood up).

🤖 Generated with Claude Code

[github-actions]

🔍 Hypatia Security Scan

Findings: 13 issues detected

Severity	Count
🔴 Critical	2
🟠 High	3
🟡 Medium	8

⚠️ Action Required: Critical security issues found!

View findings

[
  {
    "reason": "Issue in quality.yml",
    "type": "missing_workflow",
    "file": "quality.yml",
    "action": "create",
    "rule_module": "workflow_audit",
    "severity": "high"
  },
  {
    "reason": "Issue in mirror.yml",
    "type": "missing_workflow",
    "file": "mirror.yml",
    "action": "create",
    "rule_module": "workflow_audit",
    "severity": "high"
  },
  {
    "reason": "Issue in security-policy.yml",
    "type": "missing_workflow",
    "file": "security-policy.yml",
    "action": "create",
    "rule_module": "workflow_audit",
    "severity": "medium"
  },
  {
    "reason": "Action hyperpolymath/standards/.github/workflows/governance-reusable.yml@main needs attention",
    "type": "unpinned_action",
    "file": "governance.yml",
    "action": "pin_sha",
    "rule_module": "workflow_audit",
    "severity": "high"
  },
  {
    "reason": "believe_me undermines formal verification (2 occurrences, CWE-704)",
    "type": "believe_me",
    "file": "/home/runner/work/hypatia/hypatia/src/abi/RuleEngine.idr",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "critical"
  },
  {
    "reason": "Nickel file missing SPDX-License-Identifier header (1 occurrences, CWE-1104)",
    "type": "ncl_missing_spdx",
    "file": "/home/runner/work/hypatia/hypatia/configs/config.ncl",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "medium"
  },
  {
    "reason": "unsafe block -- requires SAFETY comment (22 occurrences, CWE-676)",
    "type": "unsafe_block",
    "file": "/home/runner/work/hypatia/hypatia/clients/rust/hypatia-client/src/ffi.rs",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "medium"
  },
  {
    "reason": "as_ptr exposes raw pointer that may dangle or alias unsafely (10 occurrences, CWE-676)",
    "type": "as_ptr",
    "file": "/home/runner/work/hypatia/hypatia/clients/rust/hypatia-client/src/ffi.rs",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "medium"
  },
  {
    "reason": "expect() in hot path (1 occurrences, CWE-754)",
    "type": "expect_in_hot_path",
    "file": "/home/runner/work/hypatia/hypatia/adapters/src/codeberg.rs",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "medium"
  },
  {
    "reason": "expect() in hot path (1 occurrences, CWE-754)",
    "type": "expect_in_hot_path",
    "file": "/home/runner/work/hypatia/hypatia/adapters/src/radicle.rs",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "medium"
  }
]

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