feat: kill conversations on off-platform and seller pushes

Seller detection on replies was a case-insensitive substring match over the
configured keyword list, and every hit landed in `human-required` alongside
genuine prospects that need a person. Off-platform pushes were only checked
for r4r policy modes, as were the under-18 signals.

Three layers now:

- New `off-platform-signals` module matches on normalized text (unicode
  folding, zero-width stripping, leet mapping, separator removal), so
  `0nlyf4ns`, `t3l3gr4m` and `t e l e g r a m` are caught. Ambiguous terms
  need context: `snap` on its own stays a photo request, never a kill.
- New terminal `killed` automation status. It records the evidence, sets the
  durable seller flag, supersedes the pending claim, and resolves triage to
  `done`, so killed conversations leave every actionable queue. Off-platform
  kills are independent of `reddit.filterSellers`.
- Optional AI screening of inbound replies behind
  `conversations.aiReplyScreening` (off by default). Runs only after the
  deterministic gates pass, memoizes per inbound event, and fails open.

Under-18 and in-person/contact-detail signals now apply to every policy mode
rather than r4r only, and remain human handoffs rather than kills.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/config/index.ts

@@ -123,6 +123,30 @@ export const ConfigSchema = z.object({
         'justfor.fans',
       ]),
   }),
+  conversations: z.object({
+    /**
+     * Ends a conversation outright when the other party pushes it to another
+     * app, to contact details, or to a payment rail. This is a safety control
+     * rather than a lead-quality filter, so it is independent of
+     * `reddit.filterSellers`.
+     */
+    offPlatformKill: z.boolean().default(true),
+    /** Whether a configured seller keyword or domain also ends the conversation. */
+    killOnSellerKeyword: z.boolean().default(true),
+    /**
+     * Second-stage AI screening of inbound replies. Runs only when the
+     * deterministic rules come up clean, and fails open.
+     */
+    aiReplyScreening: z.object({
+      enabled: z.boolean().default(false),
+      killConfidence: z.number().min(0).max(1).default(0.8),
+      flagConfidence: z.number().min(0).max(1).default(0.6),
+    }).default({ enabled: false, killConfidence: 0.8, flagConfidence: 0.6 }),
+  }).default({
+    offPlatformKill: true,
+    killOnSellerKeyword: true,
+    aiReplyScreening: { enabled: false, killConfidence: 0.8, flagConfidence: 0.6 },
+  }),
   openrouter: z.object({
     apiKey: z.string(),
     imageAnalysisModel: z.string().default('google/gemini-3-flash-preview'),