Pavel/add tabnine cli support (#1503)

* feat: add Tabnine CLI agent support

Tabnine CLI is a Gemini fork that uses TOML commands with the
.tabnine/agent/ directory structure and TABNINE.md context files.

Changes:
- Add 'tabnine' to AGENT_CONFIG in __init__.py
- Update release scripts (bash + PowerShell) for TOML command generation
- Update agent context scripts (bash + PowerShell)
- Add to GitHub release packages
- Update README.md and AGENTS.md documentation
- Bump version to 0.1.14
- Add 8 new tests for cross-file consistency

* fix: add missing generic to agent-context script usage string