chore: track .env.example (Task Master template, no secrets)

The .gitignore had three competing rules — .env.* (line 70), *.env.*
(line 259), and a stale negation !.env.example (line 71) that lost to
the later rules. Adding the negation at the end of the file so it wins.

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

.env.example

@@ -0,0 +1,12 @@
+# API Keys (Required to enable respective provider)
+ANTHROPIC_API_KEY="your_anthropic_api_key_here"       # Required: Format: sk-ant-api03-...
+PERPLEXITY_API_KEY="your_perplexity_api_key_here"     # Optional: Format: pplx-...
+OPENAI_API_KEY="your_openai_api_key_here"             # Optional, for OpenAI models. Format: sk-proj-...
+GOOGLE_API_KEY="your_google_api_key_here"             # Optional, for Google Gemini models.
+MISTRAL_API_KEY="your_mistral_key_here"               # Optional, for Mistral AI models.
+XAI_API_KEY="YOUR_XAI_KEY_HERE"                       # Optional, for xAI AI models.
+GROQ_API_KEY="YOUR_GROQ_KEY_HERE"                     # Optional, for Groq models.
+OPENROUTER_API_KEY="YOUR_OPENROUTER_KEY_HERE"         # Optional, for OpenRouter models.
+AZURE_OPENAI_API_KEY="your_azure_key_here"            # Optional, for Azure OpenAI models (requires endpoint in .taskmaster/config.json).
+OLLAMA_API_KEY="your_ollama_api_key_here"             # Optional: For remote Ollama servers that require authentication.
+GITHUB_API_KEY="your_github_api_key_here"             # Optional: For GitHub import/export features. Format: ghp_... or github_pat_...

.gitignore

@@ -324,3 +324,7 @@ dev-debug.log
 .taskmaster/state.json
 .taskmaster/reports/
 
+# Always track .env.example (template, no secrets) — must come AFTER the
+# .env.* / *.env.* rules above which would otherwise re-ignore it.
+!.env.example
+