Rewrite onboarding prose to a neutral voice

Justfile

@@ -53,7 +53,7 @@ check-gitea:
     @echo "[check-gitea] GET $FORGE_GITEA_URL/api/v1/version"
     @curl -fsS --max-time 10 ${FORGE_INSECURE_TLS:+-k} "$FORGE_GITEA_URL/api/v1/version" \
         | python3 -c 'import json,sys; d=json.load(sys.stdin); print("[check-gitea] Gitea version:", d.get("version","?"))'
-    @echo "[check-gitea] OK -- you can reach Gitea."
+    @echo "[check-gitea] OK: Gitea reachable."
 
 # Browser OAuth2 (PKCE) login. Reuses a live token; runs the flow otherwise.
 login:
@@ -91,12 +91,12 @@ check-access:
       DISPLAY='' WAYLAND_DISPLAY='' \
       git ls-remote "$FORGE_ORCHESTRATOR_REPO_URL" HEAD >/dev/null 2>&1 \
     && { \
-        echo "[check-access] OK -- you can reach the orchestrator."; \
+        echo "[check-access] OK: orchestrator reachable."; \
     } || { \
         echo "[check-access] FAILED. Likely causes:"; \
-        echo "  - you have not run 'just login' yet"; \
-        echo "  - your refresh token expired; run 'just relogin'"; \
-        echo "  - your Gitea account is not yet in the org"; \
+        echo "  - 'just login' has not completed yet"; \
+        echo "  - stored refresh token expired; run 'just relogin'"; \
+        echo "  - Gitea account is not yet in the org"; \
         echo "  - FORGE_ORCHESTRATOR_REPO_URL in .env is wrong"; \
         exit 1; \
     }
@@ -141,7 +141,7 @@ next-steps *args:
 run-next-steps *args:
     @bash scripts/next_steps.sh --run {{args}}
 
-# Remove the credential helper and our fields from client-auth.json.
+# Remove the credential helper and repo-managed fields from client-auth.json.
 uninstall:
     @bash scripts/uninstall.sh