feat(tui): allow navigating above launch directory

[ShivamB25]

Summary

• allow left-arrow navigation at the launch directory to rescan and open its parent directory
• preserve existing behavior for device mode and archive browsing while adding parent traversal for normal directories
• update TestMoveLeftRight to validate moving above the initial directory in an isolated temp working tree

Verification

• golangci-lint run
• go test -v -covermode=count ./...
• go test -v -race -covermode=atomic -coverprofile=coverage.out ./...

Fixes #481

[codecov]

Codecov Report

❌ Patch coverage is 80.95238% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.54%. Comparing base (ede21d2) to head (aa604e4).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
cmd/gdu/app/app.go	50.00%	1 Missing and 1 partial ⚠️
tui/tui.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #494      +/-   ##
==========================================
+ Coverage   81.42%   81.54%   +0.11%     
==========================================
  Files          49       49              
  Lines        5126     5179      +53     
==========================================
+ Hits         4174     4223      +49     
- Misses        816      820       +4     
  Partials      136      136              

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[ShivamB25]

Addressed the remaining Codecov patch gaps for tui/keys.go and pushed commit 144bc58.

What changed:

• added a focused test for the parent-analysis error path: TestAnalyzeParentOfTopDirShowsErrorWhenAnalyzeFails
• introduced a small test hook (analyzeParentPath) so the error branch in analyzeParentOfTopDir can be exercised deterministically

Validation run locally:

• golangci-lint run
• go test -v -covermode=count ./...
• go test -v -race -covermode=atomic -coverprofile=coverage.out ./...

Note: one parallel verification run hit a pre-existing Badger testdir lock contention in pkg/analyze; rerunning sequentially passed cleanly.

[dundee]

Nice PR! I think we should put this behind a config option (could be probably just config file option, not the Gdu command flag) and default it to "disabled".

[ShivamB25]

@dundee check

[dundee]

Thank you!