feat(13-12): G-B1/G-B2 cloud-egress secret scan and turn-minimality screen

assistant/egress.rs: screen_outbound(body, ctx) -> EgressVerdict runs on
every request body about to leave this node for a cloud backend. G-B1
scan_secret_shapes checks for macaroon-shaped hex runs, BIP39-length word
runs, ecash/Nostr-key-shaped strings, and the literal contents of files
under data_dir/secrets — a hit fails closed (BlockFallBackLocal), logging
only the match's kind, never the value. G-B2 assert_turn_minimal checks the
outbound body against a mechanical allowlist of this turn's own fields (the
user's turn, this turn's granted tool names, this turn's own tool results);
an unrelated earlier tool result or content wrapped for a different turn is
truncated out rather than eyeballed. An unparsable/ambiguous body also fails
closed. MAX_OUTBOUND_CONTEXT_CHARS caps body size independent of minimality.

Wired into backends/claude.rs's send() before the outbound HTTP request (on
a block, send() errors before anything is sent — Rule 3, outside this
task's originally-declared file list but structurally required to give
screen_outbound a real caller); never wired into ollama.rs — nothing leaves
the node on that leg, so paying the scan cost would be pointless.

mod.rs: AssistantCounters/OwnerNotice — grant refusals, validation
failures, turns-per-request, untrusted-content-present,
cloud-escalation-while-local-up, blocked-egress and MAX_TURNS-reached
counters, each raising an owner_notice() at its own AI-SPEC §7b threshold.
Local and owner-facing only: no exporter, no /metrics, no OTLP anywhere in
assistant/ or rate_limit.rs. backends/mod.rs's select_backend raises a
cloud-escalation-while-local-up notice when Ollama is reachable but its
configured model isn't tool-capable (Rule 3, same file-scope reasoning).

9/9 assistant::egress:: tests pass in this task's own isolated state
(Task 1's 56 plus these 9 — ToolExecCtx's counters field and its loop_.rs
call sites are Task 3's own commit, since nothing in this task's behavior
needs them yet).

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

core/archipelago/src/assistant/backends/mod.rs

@@ -137,6 +137,12 @@ pub async fn select_backend(data_dir: &Path) -> (Box<dyn Backend>, BackendId) {
             model,
             "D-04: Ollama detected but the configured model is not tool-capable — falling through to Claude"
         );
+        // G-B3/T-13-83: Ollama IS up (reachable) — this is exactly the
+        // "cloud used even though local is up" case the owner must see,
+        // even though the reason this time is capability, not health.
+        crate::assistant::global_counters().note_cloud_escalation_while_local_up(&format!(
+            "Ollama is reachable but its configured model ({model}) is not tool-capable"
+        ));
     }
     (
         Box::new(claude::ClaudeBackend::new(data_dir.to_path_buf())),