Claude Code: Fix env override bug - use empty defaults for Space secrets

The .env.example had placeholder values (hf_xxx...) that overrode real HF_TOKEN
from Space secrets when entrypoint.sh sourced the .env file. Changed to empty
values so Space environment variables take precedence.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.env.example

@@ -38,7 +38,9 @@ OPENCLAW_PASSWORD=huggingclaw
 #
 # [REQUIRED]
 #
-HF_TOKEN=hf_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+# [REQUIRED] - Must be set as Space Repository Secret
+# Leave empty here - value comes from HF Space secrets
+HF_TOKEN=
 
 # Target Dataset repository for data backup.
 # Format: your-username/repo-name
@@ -50,7 +52,9 @@ HF_TOKEN=hf_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
 #
 # [REQUIRED in manual mode, OPTIONAL in auto mode]
 #
-OPENCLAW_DATASET_REPO=your-username/HuggingClaw-data
+# [REQUIRED] - Must be set as Space Repository Secret
+# Leave empty here - value comes from HF Space settings
+OPENCLAW_DATASET_REPO=
 
 # Whether to auto-create the Dataset repo if it doesn't exist.
 # When true: HuggingClaw creates a PRIVATE dataset repo on first startup.
@@ -82,7 +86,9 @@ OPENCLAW_DATASET_REPO=your-username/HuggingClaw-data
 #
 # [RECOMMENDED] At least one of the following for AI conversations
 #
-OPENAI_API_KEY=sk-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+# [RECOMMENDED] - Must be set as Space Repository Secret
+# Leave empty here - value comes from HF Space secrets
+OPENAI_API_KEY=
 
 # Optional: base URL for OpenAI-compatible API (default: https://api.openai.com/v1)
 # Examples: https://openrouter.ai/api/v1, http://localhost:11434/v1 (Ollama), etc.
@@ -91,7 +97,9 @@ OPENAI_API_KEY=sk-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
 
 # OpenRouter — one key, 200+ models, free tier: https://openrouter.ai/keys
 #
-OPENROUTER_API_KEY=sk-or-v1-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+# [RECOMMENDED] - Must be set as Space Repository Secret
+# Leave empty here - value comes from HF Space secrets
+OPENROUTER_API_KEY=
 
 # Other providers (OpenClaw reads these from the environment)
 #