feat(installer): Tauri bootstrap installer for first-time onboarding

Hermes-Setup.exe is a small signed Rust+Tauri binary that drives
scripts/install.ps1 stage-by-stage with a native UI matching the
desktop's design language. Replaces the chicken-and-egg pattern of
shipping a 200MB Electron app whose first launch existed only to
run install.ps1.

The architecture:

  Rust backend (src-tauri/):
    bootstrap.rs        orchestrator -- Tauri commands, stage iteration
    install_script.rs   resolve install.ps1 (dev checkout, cache, GitHub raw)
    powershell.rs       spawn powershell, line-stream stdout/stderr, parse JSON
    events.rs           BootstrapEvent types -- mirror bootstrap-runner.cjs
    paths.rs            HERMES_HOME resolution + tracing log setup
    build.rs            bakes BUILD_PIN_COMMIT / BUILD_PIN_BRANCH from
                        'git rev-parse HEAD' at compile time

  React frontend (src/):
    Tauri webview rendering 4 screens (welcome / progress / success /
    failure), driven by nanostores subscribing to the Rust event stream.
    Visual layer reuses the desktop's styles.css wholesale via @import
    so the installer and desktop never drift visually.

  Distribution:
    targets = ['app', 'dmg', 'appimage'] -- no NSIS/MSI wrapper. The
    raw target/release/Hermes-Setup.exe IS the artifact on Windows;
    .dmg + .app on macOS; AppImage on Linux. One file, double-click,
    no installer-installing-an-installer pattern.

  Compile-time pinning:
    build.rs reads 'git rev-parse HEAD' and emits
    cargo:rustc-env=BUILD_PIN_COMMIT=<sha> + BUILD_PIN_BRANCH=<branch>.
    bootstrap.rs's option_env!() picks these up so the binary fetches
    install.ps1 from the exact SHA it was tested against. CI / release
    builds can override via HERMES_BUILD_PIN_COMMIT env var.

  Windows manifest:
    hermes-setup.manifest declares level='asInvoker' so the
    productName 'Hermes Setup' doesn't trip Windows's installer-
    detection heuristic and refuse to launch without elevation.
    Also declares PerMonitorV2 DPI + UTF-8 active code page + Common
    Controls v6.

Limitations of this initial version:

  * No code signing -- Windows SmartScreen will warn once on Hermes-Setup.exe
    ('More info -> Run anyway'). The downstream binaries it produces
    (Hermes.exe in win-unpacked/, the hermes CLI) are locally-built and
    therefore don't carry MOTW, so they launch without SmartScreen
    intervention. Cert procurement tracked separately.

  * macOS and Linux build paths defined but untested -- Windows-only V1.

apps/bootstrap-installer/src/components/button.tsx

@@ -0,0 +1,80 @@
+import { cva, type VariantProps } from 'class-variance-authority'
+import { Slot } from 'radix-ui'
+import * as React from 'react'
+
+import { cn } from '../lib/utils'
+
+/*
+ * Button — copied verbatim from apps/desktop/src/components/ui/button.tsx.
+ *
+ * We import the desktop's local shadcn-style Button rather than
+ * @nous-research/ui's <Button>, because the DS Button uses bg-midground /
+ * text-background-base utilities that resolve to the DS's hardcoded
+ * gold/brown brand defaults (#ffac02 / #170d02) unless overridden in
+ * runtime. The desktop never sets those vars; it routes through its
+ * own --dt-* token chain via shadcn classes like bg-primary. We do
+ * the same so visuals match exactly.
+ */
+
+const buttonVariants = cva(
+  "inline-flex shrink-0 items-center justify-center gap-2 rounded-md text-sm font-medium whitespace-nowrap transition-all outline-none focus-visible:border-ring focus-visible:ring-[0.1875rem] focus-visible:ring-ring/50 disabled:pointer-events-none disabled:opacity-50 aria-invalid:border-destructive aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
+  {
+    variants: {
+      variant: {
+        default: 'bg-primary text-primary-foreground hover:bg-primary/90',
+        destructive:
+          'bg-destructive text-white hover:bg-destructive/90 focus-visible:ring-destructive/20 dark:bg-destructive/60 dark:focus-visible:ring-destructive/40',
+        outline:
+          'border bg-background shadow-xs hover:bg-accent hover:text-accent-foreground dark:border-input dark:bg-input/30 dark:hover:bg-input/50',
+        secondary:
+          'bg-secondary text-secondary-foreground hover:bg-secondary/80',
+        ghost:
+          'hover:bg-accent hover:text-accent-foreground dark:hover:bg-accent/50',
+        link: 'text-primary underline-offset-4 decoration-current/20 hover:underline'
+      },
+      size: {
+        default: 'h-9 px-4 py-2 has-[>svg]:px-3',
+        xs: "h-6 gap-1 rounded-md px-2 text-xs has-[>svg]:px-1.5 [&_svg:not([class*='size-'])]:size-3",
+        sm: 'h-8 gap-1.5 rounded-md px-3 has-[>svg]:px-2.5',
+        lg: 'h-10 rounded-md px-6 has-[>svg]:px-4',
+        icon: 'size-9',
+        'icon-xs':
+          "size-6 rounded-md [&_svg:not([class*='size-'])]:size-3",
+        'icon-sm': 'size-8',
+        'icon-lg': 'size-10'
+      }
+    },
+    defaultVariants: {
+      variant: 'default',
+      size: 'default'
+    }
+  }
+)
+
+interface ButtonProps
+  extends React.ComponentProps<'button'>,
+    VariantProps<typeof buttonVariants> {
+  asChild?: boolean
+}
+
+export function Button({
+  className,
+  variant = 'default',
+  size = 'default',
+  asChild = false,
+  ...props
+}: ButtonProps) {
+  const Comp = asChild ? Slot.Root : 'button'
+
+  return (
+    <Comp
+      className={cn(buttonVariants({ variant, size }), className)}
+      data-size={size}
+      data-slot="button"
+      data-variant={variant}
+      {...props}
+    />
+  )
+}
+
+export { buttonVariants }