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### Requirement: Translation Guidance Options
The translate command SHALL support optional source language, glossary file, and
inline context guidance that is included in the translation prompt without
changing subtitle timing or file discovery behavior.
#### Scenario: glossary file is included in prompt
- **GIVEN** the user provides `--glossary glossary.txt`
- **WHEN** the command builds the translation prompt
- **THEN** the command SHALL read `glossary.txt` as a UTF-8 text file
- **AND** the prompt SHALL include the file content as terminology guidance
- **AND** the command SHALL still require the AI response to use the structured
cue ID mapping
#### Scenario: missing glossary file is rejected
- **GIVEN** the user provides `--glossary missing.txt`
- **WHEN** the command validates translation inputs
- **THEN** the command SHALL return an invalid path or input error
- **AND** SHALL NOT send an AI translation request
#### Scenario: inline context is included in prompt
- **GIVEN** the user provides `--context "Use formal business tone"`
- **WHEN** the command builds the translation prompt
- **THEN** the prompt SHALL include that text as domain or tone guidance
- **AND** SHALL NOT interpret the context value as a filesystem path
#### Scenario: source language is optional
- **GIVEN** the user omits `--source-language`
- **WHEN** the command builds the translation prompt
- **THEN** the prompt SHALL request translation from the detected or unspecified
source language into the target language