docs: update GitHub Pages for ctx support

[discostu105]

Summary

• Add --ctx to the global flags table in Command Reference index
• Add "Multiple Miniservers" section to Getting Started guide
• Add ctx init options, multi-context config format example, and config resolution order to Configuration reference
• Add src/commands/ctx.rs to Architecture source table and document multi-context data layout (per-context cache/token directories, project-local config)
• Add "Multi-context" feature card to the docs landing page

Test plan

• Verify GitHub Pages renders correctly after merge
• Check all internal links resolve (context management anchor, configuration reference)
• Confirm no regressions in existing docs content

https://claude.ai/code/session_01VBkrLfuydsUdyUJg4B5VWk

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 24.68%. Comparing base (ca4d193) to head (087e546).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #105   +/-   ##
=======================================
  Coverage   24.68%   24.68%           
=======================================
  Files          17       17           
  Lines        4986     4986           
=======================================
  Hits         1231     1231           
  Misses       3755     3755           

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.