fix(docs): document lambda:InvokeFunction for code-based evaluators (#1891)

`run eval` against a code-based evaluator fails with AccessDeniedException
for callers using the documented user policy:

    Access denied when invoking Lambda function: ... User: ... is not
    authorized to perform: lambda:InvokeFunction on resource:
    arn:aws:lambda:...:function:<Agent>-eval-<evaluator>

`bedrock-agentcore:Evaluate` invokes the evaluator's Lambda under the
*caller's* identity, so the caller needs `lambda:InvokeFunction`. A
resource-based policy on the function alone does not cover it.

Neither iam-policy-user.json nor the PERMISSIONS.md Evaluation table
granted or mentioned it, because until the DeepEval/Autoevals tests
added in #1828 every eval path exercised was either `Builtin.*` or
`llm-as-a-judge` -- neither of which touches Lambda.

Scoped to `arn:*:lambda:*:*:function:*-eval-*` (partition wildcard per
the multi-partition rules in AGENTS.md) rather than `*`.

The same statement was added to the e2e-github-actions CI role, which
had no lambda:InvokeFunction on any of its 9 policies -- that is what
broke e2e shard 5 on main:
https://github.com/aws/agentcore-cli/actions/runs/30663047263/job/91263525976

Co-authored-by: jariy17 <tjariy+jariy17@users.noreply.github.com>

Author: jariy17

docs/PERMISSIONS.md

@@ -381,8 +381,15 @@ These EC2 and EFS `Describe*` actions do not support resource-level scoping, so
 | Action                                           | CLI Commands                              | Purpose                                       |
 | ------------------------------------------------ | ----------------------------------------- | --------------------------------------------- |
 | `bedrock-agentcore:Evaluate`                     | `run evals`                               | Run on-demand evaluation against agent traces |
+| `lambda:InvokeFunction`                          | `run evals`                               | Invoke code-based evaluator Lambda functions  |
 | `bedrock-agentcore:UpdateOnlineEvaluationConfig` | `pause online-eval`, `resume online-eval` | Pause or resume online evaluation             |
 
+`bedrock-agentcore:Evaluate` invokes a code-based evaluator's Lambda function using the **caller's** identity, so
+`lambda:InvokeFunction` is required on the caller when running `run eval` against a `code-based` evaluator (including
+DeepEval and Autoevals third-party evaluators). Evaluator functions are named `<AgentName>-eval-<evaluatorName>`, so the
+permission can be scoped to `arn:*:lambda:*:*:function:*-eval-*`. Builtin and `llm-as-a-judge` evaluators do not need
+this permission.
+
 ### Batch evaluation and recommendations
 
 | Action                                    | CLI Commands           | Purpose                        |

docs/policies/iam-policy-user.json

@@ -56,6 +56,12 @@
       ],
       "Resource": "*"
     },
+    {
+      "Sid": "CodeBasedEvaluatorInvocation",
+      "Effect": "Allow",
+      "Action": "lambda:InvokeFunction",
+      "Resource": "arn:*:lambda:*:*:function:*-eval-*"
+    },
     {
       "Sid": "AgentCoreResourceStatus",
       "Effect": "Allow",