docs(flake): annotate KEEP+DEP rationale (standards#102)

[hyperpolymath]

Refs standards#101 standards#102.

Per the Nix-mirror retirement campaign (Wave 5), echidnabot's flake is LOAD-BEARING (KEEP+DEP): the dev shell is the sole source of postgresql and the Rust dev-tool surface (cargo-edit, cargo-audit, cargo-outdated, cargo-tarpaulin, cargo-deny, cargo-watch, cargo-deb, cargo-generate-rpm, jq, sqlx-cli) — none of which are in the guix.scm manifest (pkg-config/rust/rust-cargo/sqlite/openssl + pinned crates) nor in the sealed Containerfile (rust:1.83 + pkg-config/libsqlite3-dev/sqlite-libs/ca-certificates).

This PR adds the rule-3 annotation so the flake's retention is self-documenting. No package-set change.

🤖 Generated with Claude Code

[github-actions]

🔍 Hypatia Security Scan

Findings: 34 issues detected

Severity	Count
🔴 Critical	11
🟠 High	7
🟡 Medium	16

⚠️ Action Required: Critical security issues found!

View findings

[
  {
    "reason": "Stale AI task file -- delete or move to docs/",
    "type": "stale",
    "file": "SONNET-TASKS.md",
    "action": "delete",
    "rule_module": "root_hygiene",
    "severity": "high"
  },
  {
    "reason": "Issue in quality.yml",
    "type": "missing_workflow",
    "file": "quality.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": "Workflow executes remote script directly (curl/wget piped to shell). Download, verify checksum/signature, then execute.",
    "type": "download_then_run",
    "file": "echidnabot.yml",
    "action": "verify_download_integrity",
    "rule_module": "workflow_audit",
    "severity": "high"
  },
  {
    "reason": "Admitted leaves proof hole (2 occurrences, CWE-704)",
    "type": "admitted",
    "file": "/home/runner/work/echidnabot/echidnabot/proofs/coq/admitted_stub.v",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "critical"
  },
  {
    "reason": "Coq admit tactic leaves goal unproven (1 occurrences, CWE-704)",
    "type": "coq_admit_tactic",
    "file": "/home/runner/work/echidnabot/echidnabot/proofs/coq/admitted_stub.v",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "critical"
  },
  {
    "reason": "believe_me undermines formal verification (1 occurrences, CWE-704)",
    "type": "believe_me",
    "file": "/home/runner/work/echidnabot/echidnabot/src/abi/Foreign.idr",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "critical"
  },
  {
    "reason": "sorry leaves proof hole (3 occurrences, CWE-704)",
    "type": "sorry",
    "file": "/home/runner/work/echidnabot/echidnabot/proofs/lean/sorry_stub.lean",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "critical"
  },
  {
    "reason": "User-defined axiom -- not verified by Lean kernel (1 occurrences, CWE-704)",
    "type": "lean_axiom",
    "file": "/home/runner/work/echidnabot/echidnabot/proofs/lean/sorry_stub.lean",
    "action": "flag",
    "rule_module": "code_safety",
    "severity": "medium"
  }
]

Powered by Hypatia Neurosymbolic CI/CD Intelligence