feat: add interactive AI TUI mode (xsql-ai & xsql ai)

[zx06]

Summary

This PR introduces the interactive AI TUI mode to xsql with a standalone binary cmd/xsql-ai and subcommand xsql ai.

Key Features:

• Interactive TUI Engine: Built using Charm Bubbletea and Lipgloss design system.
• Auto-Execute Initial Prompt: Automatically analyzes and runs initial prompt given via CLI flags.
• Strict No-Wrap Table & Column Scrolling: Prevent table border alignment breakage with horizontal column scrolling via ←/→ arrow keys.
• Row Pagination & Full Vertical View: Support 12-row pagination via PgUp/PgDn and full untruncated vertical view toggle via Ctrl+E (psql \x style).
• Execution Mode Toggle: Switch between AUTO-EXECUTE and MANUAL-APPROVE modes via Shift+Tab.

[codecov]

Codecov Report

❌ Patch coverage is 79.83368% with 291 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.95%. Comparing base (f47ad0d) to head (f418f2d).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
internal/tui/model.go	76.25%	134 Missing and 31 partials ⚠️
internal/tui/components.go	82.16%	14 Missing and 14 partials ⚠️
internal/export/exporter.go	65.67%	14 Missing and 9 partials ⚠️
internal/ai/client.go	86.57%	19 Missing and 1 partial ⚠️
cmd/xsql-ai/main.go	76.92%	10 Missing and 2 partials ⚠️
cmd/xsql/ai.go	74.46%	8 Missing and 4 partials ⚠️
internal/session/store.go	82.14%	5 Missing and 5 partials ⚠️
internal/tui/render.go	79.16%	7 Missing and 3 partials ⚠️
internal/js/engine.go	92.13%	3 Missing and 4 partials ⚠️
internal/ai/prompt.go	80.00%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #65      +/-   ##
==========================================
- Coverage   82.50%   81.95%   -0.55%     
==========================================
  Files          51       62      +11     
  Lines        4259     5687    +1428     
==========================================
+ Hits         3514     4661    +1147     
- Misses        563      773     +210     
- Partials      182      253      +71     

Flag	Coverage Δ
e2e	28.97% <29.85%> (-18.06%)	⬇️
integration	28.97% <29.85%> (-18.06%)	⬇️
unittests	74.08% <79.34%> (+1.74%)	⬆️

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[sonarqubecloud]

Quality Gate passed

Issues
20 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
1.0% Duplication on New Code

See analysis details on SonarQube Cloud