Fix wave chunk 2: thinking levels auto-populate everywhere; legacy records show the resolved level

- thinking-default.ts: defaultOrderLevel (the ordering's first supported,
  the client twin of the server's defaultThinkingLevel) + populateLevel
  (an explicit level always rides; the WRITE clamps server-side, bd68486,
  and the cross-surface signal re-reads the clamped truth; only absence
  populates from the ordering) + THINKING_LABEL shared.
- Setup dialog (item 5): per-slot thinking selectors pre-populated with
  the default-order level per picked model, editable; disabled until the
  model pick; prefillLevelFromPin keeps a stored level as-is and populates
  legacy pins from the ordering.
- Composer + agent section (item 6): fresh model picks always write a
  level: the stored one rides, absence populates; the unset state can
  never re-enter. Item 4: records with a model but no stored level display
  the RESOLVED level (ordering's first supported) instead of a dash, in
  the composer pill and the settings slot triggers/menus.
- Item 7 verified live end-to-end: an explicit level rides into the PUT,
  the server clamps, the signal re-reads, the pill shows the clamped truth.

tests/thinking-default.test.ts

@@ -0,0 +1,59 @@
+/**
+ * The default-order resolution, client-side (chunk 2): the UI populates a
+ * fresh model pick's thinking level with the SAME level the engine build
+ * runs for an unset record — first DEFAULT_THINKING_ORDER entry the model
+ * supports (Platform's interlude bd68486 moved the ordering into the core
+ * barrel exactly for this). These tests pin the helper against the
+ * server's defaultThinkingLevel semantics (src/agent/models.ts).
+ */
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+import { DEFAULT_THINKING_ORDER } from "../src/core/settings.ts";
+import { defaultOrderLevel, populateLevel } from "../components/thinking-default.ts";
+import type { ThinkingLevel } from "@earendil-works/pi-agent-core";
+
+const tl = (levels: string[]) => levels as ThinkingLevel[];
+
+describe("defaultOrderLevel — the ordering's first supported", () => {
+	it("a reasoning model taking the ladder's head (medium) resolves medium", () => {
+		assert.equal(defaultOrderLevel(tl(["minimal", "low", "medium", "high"])), "medium");
+	});
+
+	it("a model without medium falls to the NEXT order entry it supports", () => {
+		// order: medium, low, high, minimal, xhigh, max — low wins here
+		assert.equal(defaultOrderLevel(tl(["minimal", "low", "high"])), "low");
+		assert.equal(defaultOrderLevel(tl(["high", "xhigh", "max"])), "high");
+	});
+
+	it("a non-reasoning model (pi reports exactly [off]) resolves off", () => {
+		assert.equal(defaultOrderLevel(tl(["off"])), "off");
+	});
+
+	it("empty support resolves off (the server's fallback), never crashes", () => {
+		assert.equal(defaultOrderLevel(tl([])), "off");
+	});
+
+	it("the full ladder resolves its head", () => {
+		const full = tl(["off", "minimal", "low", "medium", "high", "xhigh", "max"]);
+		assert.equal(defaultOrderLevel(full), DEFAULT_THINKING_ORDER[0]);
+	});
+});
+
+describe("populateLevel — an explicit pick always rides; absence populates", () => {
+	it("a supported explicit level rides unchanged", () => {
+		assert.equal(populateLevel("high", tl(["low", "high"])), "high");
+	});
+
+	it("an UNSUPPORTED explicit level STILL rides — the write clamps server-side (bd68486), the signal re-reads the clamped truth", () => {
+		// xhigh rides even though unsupported here; never re-populated client-side
+		assert.equal(populateLevel("xhigh", tl(["minimal", "medium", "high"])), "xhigh");
+	});
+
+	it("no explicit level populates the ordering's level (the fresh-pick case)", () => {
+		assert.equal(populateLevel(undefined, tl(["low", "high"])), "low");
+	});
+
+	it("off as an explicit level rides when supported", () => {
+		assert.equal(populateLevel("off", tl(["off"])), "off");
+	});
+});