Rewrite onboarding prose to a neutral voice

scripts/setup.sh

@@ -84,7 +84,7 @@ fi
 load_env
 
 if [ -z "${FORGE_GITEA_USERNAME:-}" ]; then
-    note "FORGE_GITEA_USERNAME is blank. Enter your Gitea username exactly as it appears in your profile URL."
+    note "FORGE_GITEA_USERNAME is blank. Enter the Gitea username from the profile URL."
     new_user="$(prompt_line "Gitea username")"
     if [ -z "$new_user" ]; then
         die "no username entered: aborting. Edit .env by hand and re-run 'just setup'."
@@ -180,7 +180,7 @@ if [ "$run_login" = "1" ]; then
                 forbid any interaction. Choose one:
                   1. Drop FORGE_SETUP_YES and re-run 'just setup --headless'
                      (setup will print the authorisation URL and wait
-                     while you paste it into a browser).
+                     while the URL is pasted into a browser).
                   2. Run 'just login' once on a machine with a browser
                      to populate the stored refresh token, then re-run
                      'just setup --headless' from the headless host.
@@ -202,7 +202,7 @@ GIT_TERMINAL_PROMPT=0 GCM_INTERACTIVE=Never \
     VSCODE_GIT_ASKPASS_EXTRA_ARGS="" VSCODE_GIT_IPC_HANDLE="" \
     DISPLAY="" WAYLAND_DISPLAY="" \
     git ls-remote "$FORGE_ORCHESTRATOR_REPO_URL" HEAD >/dev/null 2>&1 \
-    || die "git ls-remote failed. Your account may not yet be in the org, or FORGE_ORCHESTRATOR_REPO_URL is wrong."
+    || die "git ls-remote failed. Account membership may be missing, or FORGE_ORCHESTRATOR_REPO_URL is wrong."
 ok "silent clone access confirmed"
 
 step "6/7  cloning the orchestrator (just clone-orchestrator)"