fix(planner): server-side model calls run on the subscription, not the metered key

The roster planner died with `400 — "Your credit balance is too low to access
the Anthropic API"` while every mission on the same machine kept running. Two
Anthropic credentials reach this server and they bill differently:
`ANTHROPIC_API_KEY` (sk-ant-api, metered, runs out) and the Claude Code
subscription token (sk-ant-oat) that every VM already uses.

`Runtime::complete` with a BARE model name — "claude-opus-4-8" — resolves to the
default provider, which is the metered key. Three server-side callers did that:
the roster planner, the Master Planner, and the claw enhancer. Missions were
never affected because `mission_runtime` deliberately sends only the
subscription token into a guest; the server had no equivalent rule.

`subscription::complete_or` is now that rule, and it is the ONE place a
subscription token becomes a provider — `evaluator::subscription_judge` had its
own copy, and two of them is how one ends up with a prefix check the other
lacks.

The `sk-ant-oat` prefix is checked rather than the variable name trusted: an
API key pasted into the OAuth slot would authenticate, work, and bill the
metered account — the same failure again, discovered weeks later.

`web_search` is carried explicitly rather than defaulted. The Master Planner and
the claw enhancer both pass `true`, and a helper that quietly dropped it would
have taken web search away from two features while every test still passed.

`validator_preflight` deliberately keeps `Runtime::complete`: it probes whatever
validator spec is configured (today `glm:glm-4.7`), and forcing it onto Anthropic
would make it prove the wrong thing. A test pins both halves — no other
server-side caller may regress to the metered key, and preflight must keep
probing the configured spec.

258 lib tests.

crates/cm-api/src/routes/planner.rs

@@ -132,7 +132,11 @@ pub async fn planner_chat(
         };
         let user_prompt = format!("{hierarchy}{topology_lock}\n\n=== CONVERSATION ===\n{convo}\n\nRespond now (JSON only).");
         let system = planner_system_for(&body.mode);
-        let raw = match runtime.complete(&system, &user_prompt, "claude-opus-4-8", 8000, true).await {
+        let raw = match crate::subscription::complete_or(
+            &runtime, &system, &user_prompt, "claude-opus-4-8", 8000, true,
+        )
+        .await
+        {
             Ok(t) => t,
             Err(e) => { yield sse(json!({"stage":"error","label":format!("Opus error: {e}")})); return; }
         };