SQLSource parameter binding doesn't support passing entire SQL queries, only scalar values - needs clearer documentation

[loukratz-bv]

Problem

When using SQLSource, it's not clear from the documentation that parameters are for binding scalar VALUES, not for injecting entire SQL query strings.

Reproduction

Given a Python tool that returns a SQL query string:

def build_query(keywords: str) -> str:
    return f"SELECT * FROM table WHERE name LIKE '%{keywords}%'"

And a SQLSource step attempting to use this query:

- type: InvokeTool
  id: build_query
  tool: my_tools.build_query
  input_bindings:
    keywords: keywords
  output_bindings:
    build_query_result: sql_query

- type: SQLSource
  id: execute_query
  connection: "awsathena+rest://..."
  query: ":sql_query"
  inputs:
    - sql_query
  outputs:
    - result_id

Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## ExpectTYP## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Expected ## Exant## Expected ##g t## Expected ## Expected ## Expected ## Expected ## res## Expected with parameterized VALUES only (e.g., WHERE id = :product_id).

Suggested Documentation Improvement

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