feat(electrobun): wire persistence — SQLite, 17 themes, font system

Persistence:
- bun:sqlite at ~/.config/agor/settings.db (WAL mode, 500ms busy_timeout)
- 4 tables: schema_version, settings, projects, custom_themes
- 5 RPC handlers: settings.get/set/getAll, projects get/set

Theme system (LIVE switching):
- All 17 themes ported from Tauri (4 Catppuccin + 7 Editor + 6 Deep Dark)
- applyCssVars() sets 26 --ctp-* vars on document.documentElement
- Parallel xterm ITheme mapping per theme
- theme-store.svelte.ts: Svelte 5 rune store, persists to SQLite

Font system:
- font-store.svelte.ts: UI/terminal font family + size
- Live CSS var application (--ui-font-family/size, --term-font-family/size)
- onTermFontChange() callback registry for terminal instances
- Persists all 4 font settings to SQLite

AppearanceSettings wired: 17-theme grouped dropdown, font steppers
Init on startup: restores saved theme + fonts from SQLite

ui-electrobun/src/bun/settings-db.ts

@@ -0,0 +1,173 @@
+/**
+ * SQLite-backed settings store for the Bun process.
+ * Uses bun:sqlite (built-in, synchronous, zero external deps).
+ * DB path: ~/.config/agor/settings.db
+ */
+
+import { Database } from "bun:sqlite";
+import { homedir } from "os";
+import { mkdirSync } from "fs";
+import { join } from "path";
+
+// ── DB path ──────────────────────────────────────────────────────────────────
+
+const CONFIG_DIR = join(homedir(), ".config", "agor");
+const DB_PATH    = join(CONFIG_DIR, "settings.db");
+
+// ── Schema ───────────────────────────────────────────────────────────────────
+
+const SCHEMA = `
+PRAGMA journal_mode = WAL;
+PRAGMA busy_timeout = 500;
+
+CREATE TABLE IF NOT EXISTS schema_version (
+  version INTEGER NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS settings (
+  key   TEXT PRIMARY KEY,
+  value TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS projects (
+  id     TEXT PRIMARY KEY,
+  config TEXT NOT NULL  -- JSON blob
+);
+
+CREATE TABLE IF NOT EXISTS custom_themes (
+  id      TEXT PRIMARY KEY,
+  name    TEXT NOT NULL,
+  palette TEXT NOT NULL  -- JSON blob
+);
+`;
+
+// ── SettingsDb class ─────────────────────────────────────────────────────────
+
+export interface ProjectConfig {
+  id: string;
+  name: string;
+  cwd: string;
+  accent?: string;
+  provider?: string;
+  profile?: string;
+  model?: string;
+  [key: string]: unknown;
+}
+
+export interface CustomTheme {
+  id: string;
+  name: string;
+  palette: Record<string, string>;
+}
+
+export class SettingsDb {
+  private db: Database;
+
+  constructor() {
+    // Ensure config dir exists before opening DB
+    mkdirSync(CONFIG_DIR, { recursive: true });
+
+    this.db = new Database(DB_PATH);
+    this.db.exec(SCHEMA);
+
+    // Seed schema_version row if missing
+    const version = this.db
+      .query<{ version: number }, []>("SELECT version FROM schema_version LIMIT 1")
+      .get();
+    if (!version) {
+      this.db.exec("INSERT INTO schema_version (version) VALUES (1)");
+    }
+  }
+
+  // ── Settings ──────────────────────────────────────────────────────────────
+
+  getSetting(key: string): string | null {
+    const row = this.db
+      .query<{ value: string }, [string]>("SELECT value FROM settings WHERE key = ?")
+      .get(key);
+    return row?.value ?? null;
+  }
+
+  setSetting(key: string, value: string): void {
+    this.db
+      .query("INSERT INTO settings (key, value) VALUES (?, ?) ON CONFLICT(key) DO UPDATE SET value = excluded.value")
+      .run(key, value);
+  }
+
+  getAll(): Record<string, string> {
+    const rows = this.db
+      .query<{ key: string; value: string }, []>("SELECT key, value FROM settings")
+      .all();
+    return Object.fromEntries(rows.map((r) => [r.key, r.value]));
+  }
+
+  // ── Projects ──────────────────────────────────────────────────────────────
+
+  getProject(id: string): ProjectConfig | null {
+    const row = this.db
+      .query<{ config: string }, [string]>("SELECT config FROM projects WHERE id = ?")
+      .get(id);
+    if (!row) return null;
+    try {
+      return JSON.parse(row.config) as ProjectConfig;
+    } catch {
+      console.error(`[settings-db] Failed to parse project config for id=${id}`);
+      return null;
+    }
+  }
+
+  setProject(id: string, config: ProjectConfig): void {
+    const json = JSON.stringify(config);
+    this.db
+      .query("INSERT INTO projects (id, config) VALUES (?, ?) ON CONFLICT(id) DO UPDATE SET config = excluded.config")
+      .run(id, json);
+  }
+
+  listProjects(): ProjectConfig[] {
+    const rows = this.db
+      .query<{ config: string }, []>("SELECT config FROM projects")
+      .all();
+    return rows.flatMap((r) => {
+      try {
+        return [JSON.parse(r.config) as ProjectConfig];
+      } catch {
+        return [];
+      }
+    });
+  }
+
+  // ── Custom Themes ─────────────────────────────────────────────────────────
+
+  getCustomThemes(): CustomTheme[] {
+    const rows = this.db
+      .query<{ id: string; name: string; palette: string }, []>(
+        "SELECT id, name, palette FROM custom_themes"
+      )
+      .all();
+    return rows.flatMap((r) => {
+      try {
+        return [{ id: r.id, name: r.name, palette: JSON.parse(r.palette) }];
+      } catch {
+        return [];
+      }
+    });
+  }
+
+  saveCustomTheme(id: string, name: string, palette: Record<string, string>): void {
+    const json = JSON.stringify(palette);
+    this.db
+      .query(
+        "INSERT INTO custom_themes (id, name, palette) VALUES (?, ?, ?) ON CONFLICT(id) DO UPDATE SET name = excluded.name, palette = excluded.palette"
+      )
+      .run(id, name, json);
+  }
+
+  // ── Lifecycle ─────────────────────────────────────────────────────────────
+
+  close(): void {
+    this.db.close();
+  }
+}
+
+// Singleton — one DB handle for the process lifetime
+export const settingsDb = new SettingsDb();