fix(installer): Theta Directory branding, visible URL/join-key fields, GUI tray, service autostart

User-reported install fixes:

- Branding: every user-facing 'SSO Manager' string now says 'Theta Directory'
  (agent logs, CLI usage, agent.yml.example, installer wizard).
- Wizard page: the URL/join-key text boxes were never shown. The layout used
  Surface.Width (0 at wizard init) instead of SurfaceWidth and combined
  WordWrap with AutoSize (mutually exclusive in VCL). Rewritten with the
  canonical Inno pattern (SurfaceWidth + ScaleY + explicit label height).
- No console window after install: the tray and helper now build as
  GUI-subsystem binaries (-H=windowsgui) in build_all.sh and
  scripts/setup-build-env.ps1. The agent stays a console app for foreground
  debugging (as a service it never shows a console).
- The daemon never came up after install: install-service now starts the
  service immediately, so the tray IPC socket exists right away and the tray
  connects instead of logging 'actively refused' until a reboot.

Verified: go build/vet/test green; tray+helper PE subsystem = GUI (2), agent =
console (3); installer compiles; tray runs silently.

scripts/setup-build-env.ps1

@@ -251,13 +251,16 @@ function Invoke-Build {
     $dist = Join-Path $RepoRoot 'dist'
     New-Item -ItemType Directory -Force -Path $dist | Out-Null
     $flags = '-s -w'
+    # The tray and helper are GUI-subsystem binaries: no console window pops up
+    # when the installer starts the tray or the service spawns the helper.
+    $guiFlags = '-s -w -H=windowsgui'
     foreach ($arch in @('amd64','arm64')) {
         $env:GOOS='windows'; $env:GOARCH=$arch; $env:CGO_ENABLED='0'
         go build "-ldflags=$flags" -o (Join-Path $dist "theta-agent-windows-$arch.exe") $RepoRoot
         if ($LASTEXITCODE -ne 0) { Write-Fail "build agent windows/$arch failed"; return }
-        go build "-ldflags=$flags" -o (Join-Path $dist "theta-agent-tray-windows-$arch.exe") (Join-Path $RepoRoot 'cmd\theta-agent-tray')
+        go build "-ldflags=$guiFlags" -o (Join-Path $dist "theta-agent-tray-windows-$arch.exe") (Join-Path $RepoRoot 'cmd\theta-agent-tray')
         if ($LASTEXITCODE -ne 0) { Write-Fail "build tray windows/$arch failed"; return }
-        go build "-ldflags=$flags" -o (Join-Path $dist "theta-agent-helper-windows-$arch.exe") (Join-Path $RepoRoot 'cmd\theta-agent-helper')
+        go build "-ldflags=$guiFlags" -o (Join-Path $dist "theta-agent-helper-windows-$arch.exe") (Join-Path $RepoRoot 'cmd\theta-agent-helper')
         if ($LASTEXITCODE -ne 0) { Write-Fail "build helper windows/$arch failed"; return }
     }
     Remove-Item Env:GOOS,Env:GOARCH,Env:CGO_ENABLED -ErrorAction SilentlyContinue