test(actors): fix actor examples missing provider fields and incorrect name

Add missing provider: field to all actor examples in examples/actors/.
Fix llm_with_tools.yaml actor name from assistants/file_analyzer to
local/assistants-file_analyzer (custom actors must use local/ namespace
and cannot contain two slashes).

Add validate-all command to helper_actor_examples.py that uses ActorLoader
to validate all examples via business logic checks. Add integration test
Validate All Actor Examples Import Without Errors to actor_examples.robot
that confirms every example in examples/actors/ can be imported without
errors.

ISSUES CLOSED: #1504

examples/actors/code_review.yaml

@@ -7,6 +7,7 @@ description: Runs a code review and merges to make the best possible.
 version: "0.0"
 
 # LLM model form is Claude Opus 4
+provider: anthropic
 model: claude-opus-4-20250514
 
 system_prompt: |

examples/actors/estimator.yaml

@@ -6,6 +6,7 @@ type: llm
 description: Generates pre-execution effort, duration, and risk estimates for implementation planning
 version: "1.0"
 
+provider: openai
 model: gpt-4
 role_hint: estimation
 context_view: strategist

examples/actors/graph_workflow.yaml

@@ -7,6 +7,7 @@ description: Test-driven development workflow with automated testing and feedbac
 version: "1.0"
 
 # LLM model for agent nodes
+provider: openai
 model: gpt-4
 
 # Graph topology

examples/actors/hierarchical_workflow.yaml

@@ -8,6 +8,7 @@ description: >-
   Multi-agent development workflow with a strategist, implementer, and
   reviewer. Each node has fine-grained LSP and tool-source control.
 version: "1.0"
+provider: openai
 model: gpt-4
 
 # Actor-level skill references

examples/actors/llm_with_tools.yaml

@@ -1,12 +1,13 @@
 # LLM Actor with Tools
 # Demonstrates an LLM actor with access to multiple tools
 
-name: assistants/file_analyzer
+name: local/assistants-file_analyzer
 type: llm
 description: Analyzes files and generates reports using file system tools
 version: "1.0"
 
 # LLM configuration
+provider: openai
 model: gpt-4-turbo
 system_prompt: |
   You are a file analysis assistant. Use the available tools to:

examples/actors/simple_graph.yaml

@@ -7,6 +7,7 @@ description: Simple document processing workflow (extract → analyze → summar
 version: "1.0"
 
 # LLM model
+provider: openai
 model: gpt-3.5-turbo
 
 # Graph topology

examples/actors/simple_llm.yaml

@@ -7,6 +7,7 @@ description: Reviews Python code for best practices, style, and potential bugs
 version: "1.0"
 
 # LLM configuration
+provider: openai
 model: gpt-4
 system_prompt: |
   You are an expert Python code reviewer. Review code for:

examples/actors/strategy_with_subplan.yaml

@@ -18,6 +18,7 @@ description: >
   using the builtin/plan-subplan tool.
 version: "1.0"
 
+provider: openai
 model: gpt-4-turbo
 context_view: strategist