v4.0.3: Translation Failure Logging Improvements

This patch focuses on observability and debugging quality for failed translation chunks.

Fixed / Improved

• Added richer per-chunk error diagnostics in TranslationService when a translation task fails:
  • contextual file key
  • chunk key sample
  • full exception trace
• Increased final-retry raw Gemini response debug log truncation from 500 to 10000 characters for better visibility into malformed or partial model output.

Why this matters

• Faster root-cause analysis for failed chunks in production and CI runs.
• Better insight into model response formatting issues without changing normal translation behavior.

Compatibility

• No breaking changes.
• No command signature or workflow changes.
• Safe patch upgrade from 4.0.2.