chore: bump dependencies

chore: bump version to 0.5.2

feat: add initial support for sandbox

feat: agent harness

fix: fix the antigravity auth issues and cleanup codes

1) Refered some logic from opencode-antigravity-auth for how to handle
   antigravity oauth correctly.
2) Split the large oauth file into modules and move into their own
   component

chore: bump depdencies and code cleanup

feat: add KODER_API_KEY/KODER_BASE_URL overrides and fix OAuth vs API…

… provider mapping

chore: refine model list output formats

feat: add oauth providers google/claude/chatgpt/antigravitiy so that …

…existing subscriptions on them could be re-used with koder

fix: token stats fallback estimation and model cost lookup

1. Add tiktoken fallback in _capture_usage when API returns no usage:
   - Estimate output tokens from result.final_output
   - Estimate input/context tokens from session history
   - Reuse session's existing _estimate_tokens method (no duplicate code)

2. Add dot-to-hyphen model name variants for litellm cost lookup:
   - Models like "claude-opus-4.5" now find "claude-opus-4-5" in litellm

3. Add comprehensive tests for all modified logic