feat(security): secret-scanner, commit-guard, llm-redaction, audit-log

- lib/secrets.ts: shared SECRET_PATTERNS + scanSecrets/redact (AWS/GitLab/GitHub/Slack tokens, private keys, JWT, generic credentials)
- lib/audit.ts: local JSONL audit (~/.config/pi-kit/audit.jsonl, 600), optional PI_KIT_AUDIT_URL POST; never logs secret values
- secret-scanner: block write/edit whose content matches a secret (complements protected-paths)
- commit-guard: enforce Conventional Commits on 'git commit -m' + scan message for secrets
- llm-redaction: redact secrets from outbound payload via before_provider_request
- audit-log: session_start + slash-command usage; wires company.json auditEndpoint into env
- config: auditEndpoint (null); package.json: npm test; test/guardrails.test.ts (16 cases, all pass)

Verified: all extensions load via pi (lib/ not loaded as extensions); npm test green.

extensions/llm-redaction.ts

@@ -0,0 +1,51 @@
+/**
+ * LLM Redaction Extension
+ *
+ * WHAT: Before each provider request, redacts secrets from the outbound
+ *       payload so tokens/keys never leave the machine in a prompt. Uses the
+ *       `before_provider_request` hook and returns a modified payload.
+ *
+ * CONFIGURE: secret patterns live in extensions/lib/secrets.ts.
+ *
+ * DISABLE: remove/rename this file from the package `extensions/` folder.
+ */
+
+import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";
+import { redact } from "./lib/secrets.ts";
+import { audit } from "./lib/audit.ts";
+
+/** Recursively redact secrets in every string within a JSON-like value. */
+function redactDeep(value: unknown, counter: { n: number }): unknown {
+	if (typeof value === "string") {
+		const cleaned = redact(value);
+		if (cleaned !== value) counter.n++;
+		return cleaned;
+	}
+	if (Array.isArray(value)) return value.map((v) => redactDeep(v, counter));
+	if (value && typeof value === "object") {
+		const out: Record<string, unknown> = {};
+		for (const [k, v] of Object.entries(value as Record<string, unknown>)) {
+			out[k] = redactDeep(v, counter);
+		}
+		return out;
+	}
+	return value;
+}
+
+export default function llmRedactionExtension(pi: ExtensionAPI) {
+	pi.on("before_provider_request", async (event) => {
+		const payload = event.payload;
+		if (!payload) return undefined;
+
+		const counter = { n: 0 };
+		// Only rewrite the message content to avoid disturbing payload metadata.
+		const messages = (payload as { messages?: unknown }).messages;
+		if (messages === undefined) return undefined;
+
+		const redactedMessages = redactDeep(messages, counter);
+		if (counter.n === 0) return undefined;
+
+		audit({ kind: "redaction", occurrences: counter.n });
+		return { ...payload, messages: redactedMessages };
+	});
+}