fix: restore v1 completion value type compatibility

[c121914yu]

What changed

• Restore legacy type discriminators on structured choices[].message.content items returned by /v1/chat/completions.
• Keep /v2/chat/completions unchanged by making the compatibility behavior opt-in and enabling it only in v1.
• Preserve the legacy precedence used by chat records: text, file, tool, interactive, then reasoning.
• Add coverage for both the v1 compatibility mode and the unchanged default behavior used by v2.

Why

The unified Agent Loop now emits field-keyed values such as { text, reasoning } and { tools } without the historical type field. v1 clients may rely on type for compatibility.

Validation

• git diff --check
• Prettier 3.8.3 check passed for all changed files
• Confirmed only the v1 route enables includeLegacyType
• Targeted Vitest could not run because dependency installation repeatedly failed on npm registry HTTP 502 responses

[github-actions]

Coverage Report

Package	Statements	Branches	Functions	Lines
Global	N/A	N/A	N/A	N/A
Service	N/A	N/A	N/A	N/A
App	15.60%	12.97%	10.62%	16.17%

[github-actions]

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🕒 Time: 2026-07-18 11:29:28 (UTC+8)