"Non-Deterministic workflow detected" error from deterministic code

🐛 **Describe the bug**
I have a minimal repro which makes the Function fail with "Non-Deterministic workflow detected" error, even if the code is completely deterministic. If I replace the RuntimeError argument string with "x", then I get the expected behavior. There is something in the exception string which triggers the undesired behavior.

🤔 **Expected behavior**
The Function should end with Failed status with the exception from the activity in the output.

☕ **Steps to reproduce**
Here is the code for a minimal repro: HTTP trigger + trivial orchestration and activity. The activity throws an exception every time. (the SAS signature is fake)

```
import logging
import azure.functions as func
import azure.durable_functions as df

bp = df.Blueprint()
logger = logging.getLogger(__name__)

# ── Trigger ────────────────────────
@bp.route(route="repro")
@bp.durable_client_input(client_name="orchestration_client")
async def http_start_repro(
req: func.HttpRequest, orchestration_client: df.DurableOrchestrationClient
) -> func.HttpResponse:
instance_id = await orchestration_client.start_new("repro_orchestrator")
logger.info(f"Started repro orchestrator with ID '{instance_id}'")
return orchestration_client.create_check_status_response(req, instance_id)

# ── Orchestrator ──────────────────
@bp.orchestration_trigger(context_name="context")
def repro_orchestrator(context: df.DurableOrchestrationContext):
try:
yield context.call_activity("repro_activity")
except Exception as e:
logger.error(f"Repro orchestrator caught: {e}")
raise

# ── Activity ──────────────────────
@bp.activity_trigger(input_name="input_data")
def repro_activity(input_data):
# The sig= value contains /, +, and = which trigger the bug.
raise RuntimeError(
"Download failed: https://example.blob.core.windows.net/container/test.file"
"?sv=2025-07-05&spr=https&st=2026-04-01T10:58:55Z"
"&se=2026-04-02T10:58:55Z&sr=b&sp=r"
"&sig=aB3dE/fG5hI+jK7lM9nO="
)

# ── function_app.py ──────────────
# Save the following as function_app.py in the same directory:

import azure.functions as func
import azure.durable_functions as df
from repro_nondeterminism import bp

app = df.DFApp(http_auth_level=func.AuthLevel.ANONYMOUS)
app.register_blueprint(bp)

```

⚡**If deployed to Azure**
I see the same behavior if deployed to Azure. Please refer to the code.

まず、提供された例外文字列と、より短い "x" との比較を使用して、function_app.py の設定で repro_nondeterminism.py の最小再現を実行します。オーケストレーションのリプレイと決定性チェックを通じてアクティビティ例外がどのように報告されるかを追跡します。ワークフローが Failed ステータスに到達し、非決定的エラーなしでアクティビティ例外を公開すれば完了です。

索引モデルが issue の本文から書いたものです。