chore(agents): drop GEMINI_API_KEY fallback from generic templates (#68)

These 11 templates are the general-purpose ones that don't depend on any
particular model at the primary level (`[model] provider = "default"`).
They also ship a secondary `[[fallback_models]]` block pointing at
`gemini-2.0-flash` with `api_key_env = "GEMINI_API_KEY"`.

That default hurts everyone who doesn't happen to have `$GEMINI_API_KEY`
set — every agent boot logs `WARN Fallback driver 'gemini' failed to
init: Missing API key`, once per turn per agent. The templates that
actually intend to use Gemini as their primary model (analyst, coder,
researcher, code-reviewer, debugger, legal-assistant, data-scientist,
academic-researcher, test-engineer) are left untouched — those
declare Gemini in `[model]`, which is an intentional design choice, not
a hidden fallback.

Users who want a Gemini fallback chain for generic agents can add
`[[fallback_models]]` themselves in `~/.librefang/workspaces/agents/...`
once they've set `$GEMINI_API_KEY`.

Removed from:
  assistant, customer-support, devops-lead, doc-writer, email-assistant,
  meeting-assistant, planner, recruiter, sales-assistant, social-media,
  writer

agents/assistant/agent.toml

@@ -77,11 +77,6 @@ TOOLS AVAILABLE:
 
 You are reliable, adaptable, and genuinely helpful. You are the user's trusted first point of contact in the LibreFang Agent OS — capable of handling most tasks directly and smart enough to delegate when a specialist would do it better."""
 
-[[fallback_models]]
-provider = "default"
-model = "gemini-2.0-flash"
-api_key_env = "GEMINI_API_KEY"
-
 [resources]
 max_llm_tokens_per_hour = 300000
 max_concurrent_tools = 10

agents/customer-support/agent.toml

@@ -71,11 +71,6 @@ TOOLS AVAILABLE:
 
 You are patient, empathetic, and solutions-focused. You turn frustrated customers into satisfied advocates."""
 
-[[fallback_models]]
-provider = "default"
-model = "gemini-2.0-flash"
-api_key_env = "GEMINI_API_KEY"
-
 [resources]
 max_llm_tokens_per_hour = 200000
 max_concurrent_tools = 5

agents/devops-lead/agent.toml

@@ -43,11 +43,6 @@ When designing pipelines:
 4. Blue-green or canary deployments
 5. Automated rollback on failure"""
 
-[[fallback_models]]
-provider = "default"
-model = "gemini-2.0-flash"
-api_key_env = "GEMINI_API_KEY"
-
 [resources]
 max_llm_tokens_per_hour = 150000
 

agents/doc-writer/agent.toml

@@ -42,11 +42,6 @@ Style guide:
 - Code examples for every non-trivial concept
 - Consistent formatting and structure"""
 
-[[fallback_models]]
-provider = "default"
-model = "gemini-2.0-flash"
-api_key_env = "GEMINI_API_KEY"
-
 [resources]
 max_llm_tokens_per_hour = 200000
 

agents/email-assistant/agent.toml

@@ -63,11 +63,6 @@ TOOLS AVAILABLE:
 
 You are thorough, discreet, and efficient. You treat every email as an opportunity to communicate clearly and build professional relationships."""
 
-[[fallback_models]]
-provider = "default"
-model = "gemini-2.0-flash"
-api_key_env = "GEMINI_API_KEY"
-
 [resources]
 max_llm_tokens_per_hour = 150000
 max_concurrent_tools = 5

agents/meeting-assistant/agent.toml

@@ -66,11 +66,6 @@ TOOLS AVAILABLE:
 
 You are organized, detail-oriented, and relentlessly focused on accountability. You turn chaotic meetings into clear outcomes."""
 
-[[fallback_models]]
-provider = "default"
-model = "gemini-2.0-flash"
-api_key_env = "GEMINI_API_KEY"
-
 [resources]
 max_llm_tokens_per_hour = 150000
 max_concurrent_tools = 5

agents/planner/agent.toml

@@ -46,11 +46,6 @@ Output format:
 ### Milestones & Timeline
 ### Open Questions"""
 
-[[fallback_models]]
-provider = "default"
-model = "gemini-2.0-flash"
-api_key_env = "GEMINI_API_KEY"
-
 [resources]
 max_llm_tokens_per_hour = 200000
 

agents/recruiter/agent.toml

@@ -64,11 +64,6 @@ TOOLS AVAILABLE:
 
 You are thorough, fair, and people-oriented. You help organizations find the right talent through ethical, efficient, and human-centered recruiting practices."""
 
-[[fallback_models]]
-provider = "default"
-model = "gemini-2.0-flash"
-api_key_env = "GEMINI_API_KEY"
-
 [resources]
 max_llm_tokens_per_hour = 150000
 max_concurrent_tools = 5

agents/sales-assistant/agent.toml

@@ -57,11 +57,6 @@ TOOLS AVAILABLE:
 
 You are strategic, persuasive, and detail-oriented. You help sales teams work smarter and close more deals."""
 
-[[fallback_models]]
-provider = "default"
-model = "gemini-2.0-flash"
-api_key_env = "GEMINI_API_KEY"
-
 [resources]
 max_llm_tokens_per_hour = 150000
 max_concurrent_tools = 5

agents/social-media/agent.toml

@@ -66,11 +66,6 @@ TOOLS AVAILABLE:
 
 You are creative, culturally aware, and strategically minded. You balance creativity with data-driven decision-making."""
 
-[[fallback_models]]
-provider = "default"
-model = "gemini-2.0-flash"
-api_key_env = "GEMINI_API_KEY"
-
 [resources]
 max_llm_tokens_per_hour = 120000
 max_concurrent_tools = 5

agents/writer/agent.toml

@@ -39,11 +39,6 @@ OUTPUT:
 - For short content (emails, messages, summaries), respond directly.
 - Adapt formatting to the target platform when specified."""
 
-[[fallback_models]]
-provider = "default"
-model = "gemini-2.0-flash"
-api_key_env = "GEMINI_API_KEY"
-
 [resources]
 max_llm_tokens_per_hour = 100000