safety + repl: opts.category for Norris + probe (Phase 7 commit #4)

Closes the last two broker call sites that flow through safety.lua.
Together with commits #1-#3, all 7 broker call sites in aish now
attribute usage to the cost accumulator under the right category.

Changes:

  safety.lua:

  - llm_probe (the YES/NO destructive checker) — broker.chat call
    gains opts.category = "probe". Captures (text, usage) via
    (reply, second) and, when opts.on_usage is provided AND the
    call succeeded, routes second through opts.on_usage(model,
    category, payload). N4 signature chain: opts already flowed
    through llm_second_opinion -> M.is_destructive from #52's
    work; opts.on_usage rides along naturally with no further
    signature change.

  - M.norris_step (Norris main broker round-trip):
      * opts to broker.chat_stream gains category = "norris"
      * probe_opts (passed to is_destructive inside the loop)
        gains on_usage = helpers.on_usage so the LLM probe's
        cost lands under "probe" too
      * on_delta wrapper adds elseif kind == "usage" branch that
        calls helpers.on_usage(payload.model, payload.category,
        payload). Coexists cleanly with the existing text (rehydrator)
        and tool_call branches.

  repl.lua:

  - Norris helpers table gains on_usage = _record_usage. The R5
    central chokepoint (commit #3) does the warn-threshold check
    AND ctx:add_usage atomically.

  - :safety check meta's probe_opts always carries on_usage now
    (independently of whether secrets_session is set). secrets-aware
    scrub_msgs/rehydrate added conditionally as before.

E2E verified against live broker (safety.llm_model = "cloud"):
  - :safety check ls -la /tmp -> 2 cloud probe calls
  - "[aish] session cost $0.000128 has crossed warn_at_dollars=$0.000100"
  - probe category visible in accumulator (would appear in :cost detail
    once commit #5 ships the meta).

Regression: test_safety 87/87, test_router_model 31/31, repl loads.

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

safety.lua

@@ -188,11 +188,21 @@ local function llm_probe(model_cfg, system, cmd, opts)
     if opts and opts.scrub_msgs then
         msgs = opts.scrub_msgs(msgs, model_cfg)
     end
-    local reply, err = broker.chat(model_cfg, msgs,
-        { max_tokens = 4, timeout_ms = PROBE_TIMEOUT_MS })
+    -- Phase 7: opts.category = "probe" tags the usage in the
+    -- accumulator so :cost detail surfaces probe spend separately.
+    -- broker.chat returns (text, usage) on success; capture as
+    -- (reply, second) and branch on reply nil-ness.
+    local reply, second = broker.chat(model_cfg, msgs,
+        { max_tokens = 4, timeout_ms = PROBE_TIMEOUT_MS, category = "probe" })
     if not reply then
         -- Broker failure → safe default: treat as YES (destructive)
-        return "YES_FAILSAFE", err
+        return "YES_FAILSAFE", second
+    end
+    -- Phase 7 (N4): route the usage payload through opts.on_usage if
+    -- the caller wired one (repl.lua's _record_usage when secrets/
+    -- cost are configured).
+    if second and opts and opts.on_usage then
+        opts.on_usage(second.model, second.category, second)
     end
     if opts and opts.rehydrate then reply = opts.rehydrate(reply) end
     local upper = reply:upper()
@@ -344,9 +354,17 @@ function M.norris_step(ctx, model_cfg, helpers, opts)
     local msgs = ctx:to_messages()
     if helpers.scrub_msgs then msgs = helpers.scrub_msgs(msgs, model_cfg) end
     local rehydrator = helpers.streaming_rehydrator and helpers.streaming_rehydrator() or nil
+    -- Phase 7: thread on_usage callback into the LLM probe via
+    -- probe_opts so destructive-check costs land in the accumulator
+    -- under the "probe" category. helpers.on_usage is repl.lua's
+    -- _record_usage (the central chokepoint with warn-threshold check).
     local probe_opts = nil
-    if helpers.scrub_msgs or helpers.rehydrate then
-        probe_opts = { scrub_msgs = helpers.scrub_msgs, rehydrate = helpers.rehydrate }
+    if helpers.scrub_msgs or helpers.rehydrate or helpers.on_usage then
+        probe_opts = {
+            scrub_msgs = helpers.scrub_msgs,
+            rehydrate  = helpers.rehydrate,
+            on_usage   = helpers.on_usage,
+        }
     end
 
     local text_parts      = {}
@@ -361,9 +379,16 @@ function M.norris_step(ctx, model_cfg, helpers, opts)
                 end
             elseif kind == "tool_call" then
                 tool_calls_seen[#tool_calls_seen + 1] = payload
+            elseif kind == "usage" then
+                -- Phase 7: route Norris's own broker usage to the
+                -- accumulator via helpers.on_usage. R5 chokepoint
+                -- (_record_usage) is what's wired in.
+                if helpers.on_usage then
+                    helpers.on_usage(payload.model, payload.category, payload)
+                end
             end
         end,
-        { tools = helpers.tools_schema() })
+        { tools = helpers.tools_schema(), category = "norris" })
     if rehydrator then
         local tail = rehydrator:flush()
         if tail ~= "" then