Python: Handle dict input for MagenticStartMessage

[tonybaloney]

Fixes #1310

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/core/agent_framework/_workflows
_magentic.py	969	244	74%	58–67, 72, 76–87, 316, 341, 346–347, 423, 427, 441, 447, 462, 542, 555, 572, 581–582, 584–586, 588, 599, 666–670, 673–677, 757–760, 763–767, 769–771, 778, 817, 864, 900–902, 904, 1011, 1047, 1056–1058, 1076–1077, 1079–1080, 1099, 1144, 1147, 1175, 1178, 1183, 1191–1195, 1201, 1219–1220, 1231–1233, 1235, 1237, 1245–1250, 1252, 1256–1257, 1260–1263, 1265–1266, 1272–1274, 1277–1278, 1283–1284, 1292, 1304–1305, 1316, 1328, 1340–1343, 1372–1373, 1378–1380, 1414, 1438, 1455, 1471, 1481, 1495, 1554, 1560–1561, 1575, 1577, 1580, 1582–1583, 1586–1587, 1591, 1594, 1615, 1650–1651, 1653, 1657–1658, 1676–1677, 1687–1688, 1703, 1708–1711, 1790–1791, 1795, 1810, 1814–1815, 1819–1820, 1837, 1840, 1864–1865, 1876, 1879–1886, 1894–1898, 1907–1908, 1962–1964, 2001, 2012, 2023–2025, 2055–2057, 2068–2070, 2083–2085, 2088–2091, 2111, 2115, 2119–2120, 2137, 2144, 2147, 2151, 2156, 2193–2196, 2207–2210, 2222–2225, 2234–2237, 2252, 2256
TOTAL	10363	1708	83%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
1276	98 💤	0 ❌	0 🔥	26.860s ⏱️

[Copilot]

Pull Request Overview

This PR adds support for handling dictionary input when starting a Magentic workflow, specifically for dictionaries containing an "input" key. The change allows the workflow to accept dictionary messages and extract the text content from the "input" field.

• Added dictionary input handling for MagenticStartMessage creation
• Extracts text from dict["input"] and converts it to a MagenticStartMessage using the existing from_string method

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[Copilot]

The dict input handling lacks validation. Consider validating that message['input'] is a string before passing it to from_string(), as the method expects a string parameter but could receive any type from the dict.

Suggested change

	elif isinstance(message, dict) and "input" in message:
	elif isinstance(message, dict) and "input" in message:
	if not isinstance(message["input"], str):
	raise TypeError(f"Expected 'input' to be a string, got {type(message['input']).__name__}")