feat: add Tabnine CLI agent support

[Pavel-tabnine]

Summary

Add Tabnine CLI as a supported AI agent. Tabnine CLI uses TOML commands, the .tabnine/agent/ directory structure, and TABNINE.md context files.

Changes

Core

• Add "tabnine" entry to AGENT_CONFIG in __init__.py (folder: .tabnine/agent/, TOML format, requires_cli: True)
• Bump version 0.1.13 → 0.1.14

Release & Packaging

• Add tabnine to ALL_AGENTS in bash and PowerShell release scripts
• Add TOML command generation cases (.tabnine/agent/commands with {{args}})
• Add tabnine template packages to GitHub release script

Agent Context Scripts

• Add TABNINE_FILE variable, switch/case entry, and auto-detect support in both bash and PowerShell scripts

Documentation

• Add Tabnine CLI to supported agents table in README.md
• Add to agents table, CLI-Based Agents list, and TOML Format section in AGENTS.md
• Add changelog entry

Tests

• 7 new consistency tests verifying tabnine across AGENT_CONFIG, release scripts, agent context scripts, and CLI help
• 1 new skills directory resolution test

All 128 tests pass. Ruff lint clean.

[github-actions]

✅ PR Approval - No Critical Issues Identified

This PR successfully adds Tabnine CLI support following all established project patterns:

What it accomplishes:

• Adds Tabnine CLI as a new supported agent with proper TOML-based configuration
• Updates all relevant documentation (README.md, AGENTS.md)
• Integrates Tabnine into release packaging for both bash and PowerShell scripts
• Updates agent context scripts to support Tabnine CLI
• Follows the same patterns as other TOML-based agents (Gemini, Qwen)

Technical correctness:

• Configuration: Properly configured in AGENT_CONFIG with correct folder structure (.tabnine/)
• Release Integration: Correctly uses toml extension and {{args}} format matching Gemini/Qwen patterns
• Cross-platform: Both bash and PowerShell scripts updated consistently
• Documentation: All agent lists and help text updated comprehensively
• Backward Compatibility: Additive changes that don't break existing functionality

The implementation demonstrates excellent adherence to existing codebase conventions and patterns. Ready for merge.

[github-actions]

Tabnine PR Bot

[Standard Risk]

What This PR Does
Adds Tabnine CLI as a first-class supported agent in spec-kit, wiring it through every required layer: AGENT_CONFIG, CommandRegistrar, bash/PowerShell release scripts, agent context scripts, GitHub release packaging, and documentation. TOML command format with {{args}} placeholder is used, consistent with how Gemini and Qwen are handled.

Assessment
This is a clean, well-executed integration. The implementation is consistent with every established pattern in the codebase, and the 8 new tests provide solid coverage of the cross-cutting concerns (config, release scripts, context scripts, CLI help). Good to merge.

Cross-Repository Impact
The tabnine-cli repo confirms the TOML command format with {{args}} and .tabnine/agent/commands/ directory structure matches the actual Tabnine CLI specification. No other repositories consume spec-kit internal Python APIs. No cross-repository impact detected.

Coaching Guidelines
All changed code complies with coaching guidelines.

What Looks Good

• The skills directory resolution for tabnine correctly follows the established <folder>/skills/ convention from AGENT_CONFIG, requiring no special-case override in AGENT_SKILLS_DIR_OVERRIDES.
• Test coverage is comprehensive and systematic: every touchpoint (AGENT_CONFIG, CommandRegistrar, bash/PowerShell scripts, GitHub release script, context scripts, CLI help) gets its own targeted assertion.
• Bash and PowerShell scripts are kept in lockstep with every change mirrored across both.

Review metadata

• Risk tier: Tier 2 (Standard)
• Files reviewed: 11
• Inline comments posted: 0
• Highest severity: None
• Cross-repo analysis: performed