feat: DH-19632: Add shortcuts to cycle stacks and panels

[gzh2003]

Part of DH-19632. Introduces keyboard navigation to cycle between and within stacks. Navigating through shortcuts activates content items and respects any existing active selections.

Ctrl + ' / Ctrl + ;: to cycle forward/backward between different stacks in the layout
Ctrl + Shift + ' / Ctrl + Shift + ;: to cycle forward/backward between tabs within the currently focused stack

Changes:

• CreateNavigationEvent system
• Implement stack and tab cycling handlers in PanelManager
• Add getFocusedStack() and getFocusedStackIndex() helper methods to LayoutUtils for focus detection
• Add forceFocus parameter that bypasses the normal isFocusonShow check

[codecov]

Codecov Report

Attention: Patch coverage is 16.27907% with 72 lines in your changes missing coverage. Please review.

Project coverage is 47.28%. Comparing base (431c057) to head (c516474).
Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/dashboard/src/PanelManager.ts	16.66%	45 Missing ⚠️
packages/code-studio/src/main/AppMainContainer.tsx	0.00%	16 Missing ⚠️
packages/dashboard/src/layout/LayoutUtils.ts	0.00%	10 Missing ⚠️
...es/components/src/shortcuts/NavigationShortcuts.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2458      +/-   ##
==========================================
+ Coverage   47.21%   47.28%   +0.06%     
==========================================
  Files         718      729      +11     
  Lines       39620    39919     +299     
  Branches     9914    10181     +267     
==========================================
+ Hits        18706    18875     +169     
- Misses      20903    20990      +87     
- Partials       11       54      +43     

Flag	Coverage Δ
unit	47.28% <16.27%> (+0.06%)	⬆️

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