Fix false-positive system tool parsing for quoted TOOL_NAME examples

[siewcapital]

Summary

• prevent fallback TOOL_NAME: parsing once the assistant has already emitted non-whitespace conversational text
• keep canonical ```tool block parsing unchanged, even when a response includes explanatory text first
• make canonical start detection explicit in detectToolCallStart instead of relying on tuple ordering
• add regression coverage so quoted syntax examples stay as plain assistant text

Why

When a model explains tool syntax (for example, TOOL_NAME: read_file in a normal paragraph), the parser could misclassify that quoted text as a real tool invocation. This patch narrows the fallback path to reduce those false positives while preserving standard fenced tool-call behavior.

Testing

• Added/updated unit tests in core/tools/systemMessageTools/toolCodeblocks/interceptSystemToolCalls.vitest.ts
• Local run in this environment is blocked because vitest is not installed (ERR_MODULE_NOT_FOUND)

Closes #11070

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Summary by cubic

Prevents false-positive tool calls when the assistant shows quoted TOOL_NAME examples in normal text by limiting fallback parsing to the very start of a response. Canonical ```tool code blocks still parse normally.

• Bug Fixes
  • Allow non-codeblock TOOL_NAME starts only at response start; disable once any non-whitespace assistant text appears.
  • Continue to parse canonical ```tool blocks even after conversational text.
  • Add explicit canonical-start detection with an allowNonCodeblockStarts option and regression tests to keep quoted examples as plain text.

^{Written for commit 059a085. Summary will update on new commits.}

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[cubic-dev-ai]

No issues found across 3 files

[Co-Messi]

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[Co-Messi]

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