fix: REPL — ask/serve/registry routées vers am au lieu du shell système

is_am_command() ne connaissait pas ask/serve/registry : le REPL les
envoyait au shell système ('command not found'). Ajout aux trois
points de contact (is_am_command, COMMAND_DESCRIPTIONS, banner) +
test élargi. Docs alignées sur v1.0 : README (ask/providers/registry/
serve), ROADMAP v2.3 (v0.7.0 + v1.0.0 livrés), ARCHITECTURE (arbre src
+ section copilote & plateforme), tips ask/serve/registry. Version 1.0.2,
man pages régénérées. CI release : cross-compile Linux musl + Windows
mingw sur un seul runner, macOS optionnel.

scripts/build-release.ps1

@@ -12,9 +12,18 @@ $zip = "dist/am-windows-x86_64.zip"
 Remove-Item $zip -ErrorAction SilentlyContinue
 Compress-Archive -Path target/release/am.exe -DestinationPath $zip
 
+function Get-Sha256Net([string]$path) {
+    $stream = [System.IO.File]::OpenRead($path)
+    try {
+        $sha = [System.Security.Cryptography.SHA256]::Create()
+        $bytes = $sha.ComputeHash($stream)
+        return ([BitConverter]::ToString($bytes) -replace '-', '').ToLower()
+    } finally { $stream.Close() }
+}
+
 Write-Host ""
 Write-Host "Artefacts:"
-Get-ChildItem dist | ForEach-Object {
-    $hash = (Get-FileHash $_.FullName -Algorithm SHA256).Hash.ToLower()
+Get-ChildItem dist -File | ForEach-Object {
+    $hash = Get-Sha256Net $_.FullName
     Write-Host ("  {0,-32} {1}  sha256:{2}" -f $_.Name, $_.Length, $hash)
 }