fix(bedrock): preserve reasoning signature on Converse interleaved-thinking replay

[fesalfayed]

What does this PR do?

Fixes the AWS Bedrock (Converse API) analog of #35975 / #35586: signed Claude extended-thinking blocks were not round-tripped, so multi-turn agentic turns with interleaved thinking + tool_use silently lost their reasoning (and replaying reasoning without its original signature is rejected by Bedrock).

Root cause (three defects).

1. Wrong schema key. normalize_converse_response read reasoningContent.text, but the Converse schema nests it at reasoningContent.reasoningText.{text, signature} (botocore ReasoningContentBlock / ReasoningTextBlock). On a real Bedrock response reasoning.get("text") is always "", so nothing was captured. The fix in 8d363f8 (fix(bedrock): preserve reasoningContent in normalized responses #20366/fix(bedrock): preserve reasoningContent in normalized responses #21202) only passed because its fixture used a flattened shape that does not match AWS.
2. Signature dropped. reasoningText.signature was never read. AWS requires it on replay: "include the text and its signature unmodified."
3. Replay never reconstructs reasoningContent. convert_messages_to_converse rebuilt assistant turns as [text][toolUse] only.

Fix. Read reasoningText.{text, signature}, carry it verbatim through the existing reasoning_details channel (same mechanism AnthropicTransport uses — no new state column), and re-emit the reasoningContent block ahead of tool_use on replay. Streaming deltas (flat shape) now also retain the signature.

How was it tested?

• New TestReasoningSignatureRoundTrip (normalize → reasoning_details → replay, asserting order + signature). Fails on main (reasoning is None), passes here.
• Corrected the test_raw_reasoning_content_response fixture to the real nested schema; added a provider_data["reasoning_details"] assertion.
• tests/agent/test_bedrock_adapter.py + tests/agent/transports/: 435 passed, 0 regressions.

Closes #36260. Native-endpoint counterpart: #35586. Builds on the reasoningContent work in 8d363f8.

[fesalfayed]

Validation refresh:

• ruff check . ✅
• python scripts/check-windows-footguns.py --all ✅
• python -m pytest tests/agent/test_bedrock_adapter.py tests/agent/transports/test_bedrock_transport.py -q -o addopts='' → 139 passed
• git diff --check origin/main...HEAD ✅

Why this remains needed after the Anthropic fixes: those preserve Anthropic thinking/tool_use order, but Bedrock Converse uses reasoningContent.reasoningText.{text, signature}. Current main still reads reasoningContent.text and does not propagate the signature into provider replay data, so signed Bedrock reasoning is dropped before multi-turn replay.

[teknium1]

Thanks for identifying the real Converse schema and the missing signature path. Current main still reads the flattened key at agent/bedrock_adapter.py:705-710 and emits no replayed reasoning blocks at agent/bedrock_adapter.py:603-626.

Problems

• agent/bedrock_adapter.py:557-581 reconstructs all reasoning_details before all tool calls. For the interleaved signed-thinking case in this PR's title, this changes [reasoning_1, tool_1, reasoning_2, tool_2] into [reasoning_1, reasoning_2, tool_1, tool_2]. The project’s native Anthropic implementation records an ordered-block channel for exactly this loss of cross-type ordering (agent/transports/anthropic.py:167-183; tests/agent/test_anthropic_thinking_block_order.py:9-29).

Suggested changes

• Preserve and replay an ordered Bedrock block sequence when signed reasoning and tool uses coexist, rather than reconstructing from parallel lists.
• Add a round-trip regression with two signed reasoning blocks separated by tool uses; the current new test covers only one leading reasoning block.

Automated hermes-sweeper review.

[teknium1]

This front-loads every reasoning block before the separate tool-call loop below. For an interleaved signed response [reasoning_1, tool_1, reasoning_2, tool_2], replay becomes [reasoning_1, reasoning_2, tool_1, tool_2], invalidating the positional guarantee this PR targets. Preserve an ordered Bedrock block sequence instead of reconstructing from parallel lists.