fix: the knowledge-context slider is a discrete 6-stop scale — off, then powers of four from 64

The continuous 0-4096 dial was precision theater (a 128-token budget is
~2 propositions; nobody wants that granularity). Decided stops (owner,
2026-09-15): 0 / 64 / 256 / 1024 / 4096 / 16384 — the native range walks
positions 0-5 and maps through GRAPH_CONTEXT_TOKENS_STOPS in contracts.
Max rises to 16384 (route range follows); the server still accepts any
integer in range so a stale client cannot brick settings; non-stop
legacy values snap to the nearest stop for the thumb, readout stays
honest.

tests/graph-context-core.test.ts

@@ -13,7 +13,7 @@ import {
 	steerDelivered,
 	GRAPH_CONTEXT_TOKENS_DEFAULT,
 	GRAPH_CONTEXT_TOKENS_MAX,
-	GRAPH_CONTEXT_TOKENS_STEP,
+	GRAPH_CONTEXT_TOKENS_STOPS,
 	graphContextText,
 	type GraphContextData,
 } from "../src/core/contracts.ts";
@@ -279,10 +279,12 @@ describe("the runner's pure gates", () => {
 		assert.equal(effectiveContextBudget({ graphContextTokens: 2048 }), 2048);
 	});
 
-	it("the decided knobs: default 1024, max 4096, step 128", () => {
+	it("the decided knobs: default 1024, max 16384, discrete powers-of-four stops from 64", () => {
 		assert.equal(GRAPH_CONTEXT_TOKENS_DEFAULT, 1024);
-		assert.equal(GRAPH_CONTEXT_TOKENS_MAX, 4096);
-		assert.equal(GRAPH_CONTEXT_TOKENS_STEP, 128);
+		assert.equal(GRAPH_CONTEXT_TOKENS_MAX, 16384);
+		// The scale revision (owner, 2026-09-15): off then powers of four —
+		// every stop a real decision, no fine-grained dial theater.
+		assert.deepEqual([...GRAPH_CONTEXT_TOKENS_STOPS], [0, 64, 256, 1024, 4096, 16384]);
 	});
 
 	it("contextToolCallId is deterministic per chat (the one-shot dedup key)", () => {

tests/render-new-session.test.tsx

@@ -102,8 +102,10 @@ describe("DraftShell — the sessionless surface", () => {
 			html.indexOf('data-testid="stats-bar"') < html.indexOf('data-testid="graph-context-control"'),
 			"the slider is the stats bar's left slot",
 		);
-		// The slider's default position: 1024 of 4096, step 128 (decided).
-		assert.ok(html.includes('min="0"') && html.includes('max="4096"') && html.includes('step="128"'));
+		// The DISCRETE slider (owner, 2026-09-15): 6 positions (off + powers of
+		// four from 64), not a continuous 0-4096 dial.
+		assert.ok(html.includes('min="0"') && html.includes('max="5"') && html.includes('step="1"'));
+		assert.ok(html.includes('value="3"'), "default 1024 = stop index 3");
 		// The readout: "tok" abbreviated, but the FULL number (owner, 2026-09-15:
 		// no k-rounding — 1024 reads as 1024).
 		assert.ok(html.includes("1024 tok"), "the readout shows the default budget, not 0 — default is ON");