Auditor scaffold: types + Gitea client + policy stub + README

All-Bun sub-agent that watches open PRs on Gitea, reads ship-claims,
and hard-blocks merges when the code doesn't back the claim. First
commit of N; this is the skeleton. Dynamic/static/inference/kb checks
+ poller land in follow-up commits on this same branch.

- auditor/types.ts — Claim, Finding, Verdict, PrSnapshot shapes
- auditor/gitea.ts — minimal API client (listOpenPrs, getPrDiff,
  postCommitStatus, postReview). Live-proven: returned 0 open PRs
  against our repo (which IS the current state — every commit today
  went to main directly, which is the problem this auditor is meant
  to prevent)
- auditor/policy.ts — stub `assembleVerdict` + severity rules.
  Intentionally conservative defaults: strong claim + zero evidence
  = block, not warn.
- auditor/README.md — how to run + the hard-block mechanism

Workflow discipline change: starting with this branch, no more
direct pushes to main. Every change lands as a PR. When this
auditor is fully built and running, it'll review its own
completion PR — the recursive self-test.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

auditor/policy.ts

@@ -0,0 +1,62 @@
+// ═══════════════════════════════════════════════════════════════════
+// YOU WRITE THIS FILE. Policy decides what blocks vs what's a comment.
+// Defaults are opinionated on the "stop clicking past placeholder"
+// side — easier to loosen than to tighten when you're watching the
+// auditor behave in live PRs.
+// ═══════════════════════════════════════════════════════════════════
+
+import type { Finding, Verdict } from "./types.ts";
+
+/// Translate the four-check output into a single verdict. This is the
+/// single pane of glass the auditor operates on — tune thresholds here.
+export function assembleVerdict(
+  findings: Finding[],
+  metrics: Record<string, number>,
+  pr_number: number,
+  head_sha: string,
+): Verdict {
+  const blocking = findings.filter(f => f.severity === "block");
+  const warning = findings.filter(f => f.severity === "warn");
+
+  let overall: Verdict["overall"];
+  let one_liner: string;
+
+  if (blocking.length > 0) {
+    overall = "block";
+    one_liner = `${blocking.length} blocking issue${blocking.length > 1 ? "s" : ""}: ${blocking[0].summary}`;
+  } else if (warning.length >= 3) {
+    // Three or more warnings is a block — death by a thousand cuts.
+    overall = "request_changes";
+    one_liner = `${warning.length} warnings — see review`;
+  } else if (warning.length > 0) {
+    overall = "request_changes";
+    one_liner = warning[0].summary;
+  } else {
+    overall = "approve";
+    one_liner = `all checks passed (${findings.length} findings, all info)`;
+  }
+
+  return {
+    pr_number,
+    head_sha,
+    audited_at: new Date().toISOString(),
+    overall,
+    findings,
+    metrics,
+    one_liner,
+  };
+}
+
+/// Which strength-of-claim warrants which severity when evidence is
+/// weak? A "Phase X shipped" claim with zero integration tests is a
+/// blocker. A "should work" claim with no test is a warn.
+export function severityFromClaimEvidence(
+  claim_strength: "weak" | "moderate" | "strong",
+  evidence_grade: "none" | "partial" | "full",
+): "info" | "warn" | "block" {
+  if (evidence_grade === "full") return "info";
+  if (claim_strength === "strong" && evidence_grade === "none") return "block";
+  if (claim_strength === "strong" && evidence_grade === "partial") return "warn";
+  if (claim_strength === "moderate" && evidence_grade === "none") return "warn";
+  return "info";
+}