fix(bedrock): preserve reasoningContent in normalized responses

[teknium1]

Salvage of #20366 onto current main (172 commits stale).

Bedrock thinking text now survives normalization on both raw converse() and streaming converse_stream() paths. Previously agent/bedrock_adapter.py:normalize_converse_response() didn't handle reasoningContent blocks, and the stream path only forwarded reasoning to the callback — nothing persisted onto the assistant message. The transport layer (agent/transports/bedrock.py:108) already reads msg.reasoning_content, so the field just arrived empty and NormalizedResponse.reasoning was always None even on Claude 4.6+ thinking output.

Changes

• agent/bedrock_adapter.py: collect reasoningContent.text blocks in both normalize_converse_response() and stream_converse_with_callbacks(), attach as reasoning_content on the assistant SimpleNamespace.
• tests/agent/test_bedrock_adapter.py: assert streamed reasoning persists on the normalized message, not only via callback.
• tests/agent/transports/test_bedrock_transport.py: regression coverage for raw Converse with reasoningContent.

Validation

	Before	After
NormalizedResponse.reasoning on Bedrock thinking output	None	Thinking text
tests/agent/test_bedrock_adapter.py + tests/agent/transports/test_bedrock_transport.py	-	137 passed
E2E adapter → transport chain (real imports)	reasoning lost	reasoning preserved

Authored-by: @molvikar via cherry-pick, no follow-up fixes needed.
Closes #20366

[github-actions]

🔎 Lint report: hermes/hermes-f87961d0 vs origin/main

ruff

Total: 0 on HEAD, 0 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 0 pre-existing issues carried over.

ty (type checker)

Total: 7483 on HEAD, 7483 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 3932 pre-existing issues carried over.

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