feat(compose): Task #5 — Compose from Case + URL protocol + auto-file

UI:
- ComposeFromCaseDialog (RTL, search-then-pick a single Case via
  GlobalSearch + entityType=Case filter)
- ComposeFromCaseViewModel — debounced GlobalSearch, returns chosen
  EspoEntityRef

Host:
- ComposeService.ApplyCaseToMailAsync:
  * fetches Case + primary Contact
  * stamps UserProperties EspoCaseId, EspoCaseName, OutlookAddinGuid
  * pre-fills To/Subject and appends an RTL footer with a CRM deep link
- ItemSend hook (in AddInHost.HookItemSend): when the user sends a
  tagged compose, register guid → target with SentItemsWatcher
- SentItemsWatcher: rooted Items reference (prevents GC), 30s expiry
  sweep, 2-min default timeout per pending tag, MailMatched event
- AddInHost.OnSentMailMatched: extracts the sent MailItem, files via
  FilingService, stamps "Filed: {name}" category
- LaunchComposeFromCaseAsync (Inspector ribbon) and
  LaunchComposeFromCaseByIdAsync (URL protocol) entry points
- NamedPipeListener (\.\pipe\MarcusLaw.OutlookAddin) — listens for
  "COMPOSE <caseId>" lines, dispatches on WPF Dispatcher

Ribbon:
- InspectorRibbon.xml — "כתוב מתיק" button on Mail Compose ribbon, hidden
  for received/read mail via getVisible
- ExplorerRibbon class now serves both Explorer and Inspector ribbons
  (single IRibbonExtensibility, dispatches by ribbonID)

URL protocol:
- New OutlookAddinProtocolHandler console project (net48 WinExe):
  parses outlookaddin://compose?caseId=<id>, connects to named pipe,
  writes "COMPOSE <id>\n"
- tools/install-protocol.ps1 + uninstall-protocol.ps1 register the
  scheme under HKCU\Software\Classes\outlookaddin

Core/UI/Tests + protocol handler all build; 38 unit tests still green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tools/install-protocol.ps1

@@ -0,0 +1,41 @@
+# Registers the `outlookaddin://` URL protocol in HKCU so that
+# clicking a link like `outlookaddin://compose?caseId=…` launches the
+# OutlookAddinProtocolHandler.exe shim, which forwards the request over
+# a named pipe to the running VSTO add-in.
+#
+# Usage:
+#   .\install-protocol.ps1 -ExePath "C:\Path\To\OutlookAddinProtocolHandler.exe"
+#
+# Or, to derive the path automatically from a ClickOnce install:
+#   .\install-protocol.ps1
+
+[CmdletBinding()]
+param(
+    [string]$ExePath
+)
+
+$ErrorActionPreference = 'Stop'
+
+if (-not $ExePath) {
+    $candidate = Join-Path $env:LOCALAPPDATA "Apps\OutlookAddinProtocolHandler\OutlookAddinProtocolHandler.exe"
+    if (Test-Path $candidate) {
+        $ExePath = $candidate
+    } else {
+        throw "ExePath not supplied and default location not found: $candidate"
+    }
+}
+
+if (-not (Test-Path $ExePath)) {
+    throw "Protocol handler not found: $ExePath"
+}
+
+$root = "HKCU:\Software\Classes\outlookaddin"
+New-Item -Path $root -Force | Out-Null
+Set-ItemProperty -Path $root -Name "(default)" -Value "URL:OutlookAddin Protocol"
+Set-ItemProperty -Path $root -Name "URL Protocol" -Value ""
+
+$shellCmd = Join-Path $root "shell\open\command"
+New-Item -Path $shellCmd -Force | Out-Null
+Set-ItemProperty -Path $shellCmd -Name "(default)" -Value ("`"" + $ExePath + "`" `"%1`"")
+
+Write-Host "Registered outlookaddin:// -> $ExePath" -ForegroundColor Green

tools/uninstall-protocol.ps1

@@ -0,0 +1,3 @@
+$ErrorActionPreference = 'SilentlyContinue'
+Remove-Item -Path "HKCU:\Software\Classes\outlookaddin" -Recurse -Force
+Write-Host "Removed outlookaddin:// protocol registration" -ForegroundColor Yellow