feat: workspaces shell + cwd-lsp rename + mcp/settings/system-prompt features + app wiring

- workspaces: URL-driven conversation grouping (home listing at /, routing,
  store, http adapter, WorkspaceCard) wired into the App.svelte shell
- rename features/workspace -> features/cwd-lsp (the cwd/lsp status feature)
- new features: mcp (status view), settings (chat-limit field), system-prompt
  (prompt builder), all rendered via the generic surface host
- chat: store + ChatView updates
- tabs: tabs-store updates
- app wiring: ErrorModal (full-screen error surface), app/App.svelte + store.svelte

This commit makes HEAD typecheck clean for the first time: the prior HEAD
(c95cc77) imported features/settings from app/App.svelte but never committed
the feature, so only the full working tree was green.

2 files changed, 193 insertions, 0 deletions

diff --git a/src/features/settings/ui/ChatLimitField.svelte b/src/features/settings/ui/ChatLimitField.svelte
new file mode 100644
index 0000000..9b9911a
--- /dev/null
+++ b/src/features/settings/ui/ChatLimitField.svelte
@@ -0,0 +1,104 @@
+<script lang="ts">
+	import { untrack } from "svelte";
+	import { MAX_CHAT_LIMIT, MIN_CHAT_LIMIT } from "../../../core/chunks";
+	import { chatLimitChanged, parseChatLimit, type SaveChatLimit } from "../logic/view-model";
+
+	let {
+		chatLimit,
+		save,
+	}: {
+		/** The persisted chat limit (max loaded chunks per conversation). */
+		chatLimit: number;
+		save: SaveChatLimit;
+	} = $props();
+
+	// Seed from the prop; the $effect below re-seeds on external changes (a live
+	// apply from elsewhere) but only while the field is untouched, so an in-flight
+	// change can't clobber what the user typed.
+	let value = $state("");
+	let lastSeed = $state("");
+	let saving = $state(false);
+	let error = $state<string | null>(null);
+	let justSaved = $state(false);
+	let savedValue = $state<number | null>(null);
+
+	$effect(() => {
+		const incoming = String(chatLimit);
+		untrack(() => {
+			if (value === lastSeed) value = incoming;
+			lastSeed = incoming;
+		});
+	});
+
+	const dirty = $derived(chatLimitChanged(value, chatLimit));
+
+	async function handleSave() {
+		if (saving || !dirty) return;
+		const parsed = parseChatLimit(value);
+		if (!parsed.ok) {
+			error = parsed.error;
+			return;
+		}
+		saving = true;
+		error = null;
+		justSaved = false;
+		const result = await save(parsed.value);
+		saving = false;
+		if (result.ok) {
+			justSaved = true;
+			savedValue = result.chatLimit;
+			// Reflect the clamped / persisted value back into the input immediately
+			// (the prop will also re-assert it via the effect above).
+			value = String(result.chatLimit);
+			lastSeed = value;
+		} else {
+			error = result.error;
+		}
+	}
+
+	function onInput() {
+		justSaved = false;
+		error = null;
+	}
+</script>
+
+<div class="flex flex-col gap-1">
+	<span class="text-xs font-semibold uppercase opacity-60">Chat limit</span>
+	<div class="flex items-center gap-2">
+		<input
+			type="text"
+			inputmode="numeric"
+			class="input input-bordered input-sm w-full font-mono text-xs"
+			placeholder={String(chatLimit)}
+			bind:value
+			disabled={saving}
+			oninput={onInput}
+			onkeydown={(e) => {
+				if (e.key === "Enter") handleSave();
+			}}
+			aria-label="Chat limit"
+		/>
+		<button
+			type="button"
+			class="btn btn-primary btn-sm"
+			disabled={saving || !dirty}
+			onclick={handleSave}
+		>
+			{#if saving}
+				<span class="loading loading-spinner loading-xs"></span>
+			{:else}
+				Set
+			{/if}
+		</button>
+	</div>
+	{#if error}
+		<p class="text-xs text-error">{error}</p>
+	{:else if justSaved && !dirty}
+		<p class="text-xs text-success">Saved{savedValue !== null ? `: ${savedValue}.` : "."}</p>
+	{:else}
+		<p class="text-xs opacity-50">
+			Max loaded chunks per conversation ({MIN_CHAT_LIMIT}–{MAX_CHAT_LIMIT}). Lowering it unloads
+			older history; raise it and use "Show earlier" to page back in.
+		</p>
+	{/if}
+</div>
diff --git a/src/features/settings/ui/ChatLimitField.test.ts b/src/features/settings/ui/ChatLimitField.test.ts
new file mode 100644
index 0000000..73bc449
--- /dev/null
+++ b/src/features/settings/ui/ChatLimitField.test.ts
@@ -0,0 +1,89 @@
+import { render, screen } from "@testing-library/svelte";
+import userEvent from "@testing-library/user-event";
+import { describe, expect, it } from "vitest";
+import type { ChatLimitSaveResult } from "../logic/view-model";
+import ChatLimitField from "./ChatLimitField.svelte";
+
+// A fake save that resolves ok with the value it was given.
+function fakeSave(): {
+	saves: number[];
+	last: number | null;
+	impl: (value: number) => Promise<ChatLimitSaveResult>;
+} {
+	const saves: number[] = [];
+	return {
+		saves,
+		last: null,
+		impl: async (value: number) => {
+			saves.push(value);
+			return { ok: true, chatLimit: value };
+		},
+	};
+}
+
+describe("ChatLimitField", () => {
+	it("seeds the input from the persisted limit and disables Set while unchanged", () => {
+		render(ChatLimitField, { props: { chatLimit: 256, save: fakeSave().impl } });
+		expect(screen.getByLabelText("Chat limit")).toHaveValue("256");
+		expect(screen.getByRole("button", { name: "Set" })).toBeDisabled();
+	});
+
+	it("enables Set when the typed value differs (regression: number-binding coercion)", async () => {
+		const user = userEvent.setup();
+		const save = fakeSave();
+		render(ChatLimitField, { props: { chatLimit: 256, save: save.impl } });
+
+		const input = screen.getByLabelText("Chat limit");
+		await user.clear(input);
+		await user.type(input, "10");
+
+		expect(screen.getByRole("button", { name: "Set" })).toBeEnabled();
+	});
+
+	it("keeps Set disabled for non-numeric input", async () => {
+		const user = userEvent.setup();
+		const save = fakeSave();
+		render(ChatLimitField, { props: { chatLimit: 256, save: save.impl } });
+
+		const input = screen.getByLabelText("Chat limit");
+		await user.clear(input);
+		await user.type(input, "abc");
+
+		expect(screen.getByRole("button", { name: "Set" })).toBeDisabled();
+	});
+
+	it("clicking Set calls save with the parsed value and shows the confirmation", async () => {
+		const user = userEvent.setup();
+		const save = fakeSave();
+		const { rerender } = render(ChatLimitField, {
+			props: { chatLimit: 256, save: save.impl },
+		});
+
+		const input = screen.getByLabelText("Chat limit");
+		await user.clear(input);
+		await user.type(input, "50");
+		await user.click(screen.getByRole("button", { name: "Set" }));
+
+		expect(save.saves).toEqual([50]);
+		// In the real app the reactive `chatLimit` prop updates to the saved value
+		// (the store sets it synchronously), which clears `dirty` and reveals the
+		// "Saved" badge. Rerender simulates that propagation.
+		rerender({ chatLimit: 50, save: save.impl });
+		expect(screen.getByText(/Saved/i)).toBeInTheDocument();
+	});
+
+	it("clamps a below-floor value when saving", async () => {
+		const user = userEvent.setup();
+		const save = fakeSave();
+		render(ChatLimitField, { props: { chatLimit: 256, save: save.impl } });
+
+		const input = screen.getByLabelText("Chat limit");
+		await user.clear(input);
+		await user.type(input, "5"); // clamps to MIN (10)
+		await user.click(screen.getByRole("button", { name: "Set" }));
+
+		// The save port receives the clamped value (the view-model clamps before save).
+		expect(save.saves).toEqual([10]);
+		expect(input).toHaveValue("10");
+	});
+});