feat(ai service): enhance message cleanup for provider responses

feat(gemini): update default model to gemini-2.5-flash-lite

docs(readme): update jira task style description

refactor(cmd): improve commit command logic and options

docs(readme): update feature list and flag descriptions

chore(docs): update documentation and default jira task style

feat(jira): improve jira task integration in commit messages

feat(commit): adapt git getStagedDiff to handle maximum diff size con…

…straint

- Modify git getStagedDiff to accept maxSizeBytes
- Implement size constraints in diff retrieval
- Update related tests to reflect changes in function signature