Fix system-message tools parser when tool call is non-terminal (#11092)

* fix(openai-adapters): map reasoning-delta to reasoning_content

* Fix system-message tool parser for non-terminal tool calls

* Fix duplicate predefined tools in dynamic system-message section

* fix(openai-adapters): fix TS syntax error in vercelStreamConverter test

The `as typeof X & Y` type assertion was ambiguous to the TypeScript
parser without parentheses, causing TS1005 errors across all CI checks.
Simplify to `as any` since this is a test assertion.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* chore: remove unrelated vercelStreamConverter changes

Per reviewer feedback — keeping this PR focused on the
system-message tools parser fix.

* fix: correct test expectations for post-tool-call content preservation

The 'preserves content after a tool call' test incorrectly consumed the
trailing newline and preserved text within the tool-call loop. Adjusted
the loop count from 6 to 4 (actual tool-call deltas) and added explicit
assertions for the trailing newline and preserved content chunks.

The 'mid-message' test was missing an assertion for the newline chunk
emitted between the closing codeblock fence and trailing text.

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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: MumuTW <mumu@novel98.com>