fix(ci): Prevent workflow failures in relocated adk_team samples

Workflows failed because the gemini-2.5-pro model is not available for our projects and the CONTRIBUTING.md relative path resolved incorrectly after relocation. Updated the model to gemini-3.5-flash and adjusted the path resolver depth.

Change-Id: Iffc8a2b0044f3d73b0cb0b364db220d2bd055683

Author: xuanyang15

contributing/samples/adk_team/adk_answering_agent/agent.py

@@ -38,7 +38,7 @@
 
 
 root_agent = Agent(
-    model="gemini-2.5-pro",
+    model="gemini-3.5-flash",
     name="adk_answering_agent",
     description="Answer questions about ADK repo.",
     instruction=f"""

contributing/samples/adk_team/adk_answering_agent/gemini_assistant/agent.py

@@ -72,7 +72,7 @@ def search_gemini_api_docs(queries: List[str]) -> Dict[str, Any]:
 
 
 root_agent = Agent(
-    model="gemini-2.5-pro",
+    model="gemini-3.5-flash",
     name="gemini_assistant",
     description="Answer questions about Gemini API.",
     instruction="""

contributing/samples/adk_team/adk_documentation/adk_docs_updater/agent.py

@@ -46,7 +46,7 @@
   )
 
 root_agent = Agent(
-    model="gemini-2.5-pro",
+    model="gemini-3.5-flash",
     name="adk_docs_updater",
     description=(
         "Update the ADK docs based on the code in the ADK Python codebase"

contributing/samples/adk_team/adk_issue_formatting_agent/agent.py

@@ -132,7 +132,7 @@ def list_comments_on_issue(issue_number: int) -> dict[str, any]:
 
 
 root_agent = Agent(
-    model="gemini-2.5-pro",
+    model="gemini-3.5-flash",
     name="adk_issue_formatting_assistant",
     description="Check ADK issue format and content.",
     instruction=f"""

contributing/samples/adk_team/adk_pr_triaging_agent/agent.py

@@ -41,7 +41,7 @@
 ]
 
 CONTRIBUTING_MD = read_file(
-    Path(__file__).resolve().parents[3] / "CONTRIBUTING.md"
+    Path(__file__).resolve().parents[4] / "CONTRIBUTING.md"
 )
 
 APPROVAL_INSTRUCTION = (
@@ -220,7 +220,7 @@ def add_comment_to_pr(pr_number: int, comment: str) -> dict[str, Any]:
 
 
 root_agent = Agent(
-    model="gemini-2.5-pro",
+    model="gemini-3.5-flash",
     name="adk_pr_triaging_assistant",
     description="Triage ADK pull requests.",
     instruction=f"""

contributing/samples/adk_team/adk_triaging_agent/agent.py

@@ -244,7 +244,7 @@ def change_issue_type(issue_number: int, issue_type: str) -> dict[str, Any]:
 
 
 root_agent = Agent(
-    model="gemini-2.5-pro",
+    model="gemini-3.5-flash",
     name="adk_triaging_assistant",
     description="Triage ADK issues.",
     instruction=f"""