Remove outdated API in codecompanion.nvim extension

[Davidyz]

• references to context
• CodeCompanion.Agent to CodeCompanion.Tools

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.77%. Comparing base (653374f) to head (dece3e8).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #262   +/-   ##
=======================================
  Coverage   99.77%   99.77%           
=======================================
  Files          24       24           
  Lines        1767     1767           
=======================================
  Hits         1763     1763           
  Misses          4        4           

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