Harden OperationBand index bounds and band-line parsing

[patrickrb]

Context

First fix from the pre-app-store bug bash triage ledger (PR 2 — the highest-confidence cluster of real defects). Triage-verified by reading source; these are genuine crashers reachable from the band/frequency pickers and the bands.txt asset loader.

Bugs fixed

Where	Bug	Trigger
OperationBand.getBandFreq(int)	Guard was index > size — off-by-one. index == size slipped through to bandList.get(index) → IndexOutOfBounds. Negatives unguarded.	Band picker at the list boundary
OperationBand.getBandInfo(int)	Returned bandList.get(0) when index >= size → crashes on an empty list (missing/corrupt bands.txt); negatives unguarded.	First-run / corrupt asset
OperationBand.Band(String)	A truncated line like "20m:" passes isBandLine() (it has a colon) but splits to one field → constructor throws and aborts the entire band-list load, leaving the app with no bands.	One malformed line in bands.txt

Approach

• Centralised the bounds check in a single isValidBandIndex() helper used by every accessor (rejects both negatives and index >= size).
• getBandInfo falls back to the default band when the list is empty.
• Extracted the asset parse loop into parseBandLines(), which logs and skips an individual malformed line instead of aborting the whole load.
• No behaviour change for valid input.

Tests

OperationBandTest (now 34 tests, all green) gains coverage for: the off-by-one (index == size), negative indices on both accessors, empty-list getBandInfo, and parseBandLines skipping truncated / non-numeric / comment / blank lines while keeping valid neighbours.

Run: cmd.exe /c "gradlew.bat testDebugUnitTest --tests com.bg7yoz.ft8cn.database.OperationBandTest"

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 8.32%. Comparing base (4e7fadc) to head (978c065).
⚠️ Report is 2 commits behind head on dev.

Files with missing lines	Patch %	Lines
.../java/com/bg7yoz/ft8cn/database/OperationBand.java	88.88%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##               dev    #229      +/-   ##
==========================================
+ Coverage     8.28%   8.32%   +0.03%     
- Complexity     794     802       +8     
==========================================
  Files          289     289              
  Lines        32597   32606       +9     
  Branches      5197    5199       +2     
==========================================
+ Hits          2702    2714      +12     
+ Misses       29682   29679       -3     
  Partials       213     213              

Files with missing lines	Coverage Δ
.../java/com/bg7yoz/ft8cn/database/OperationBand.java	66.34% <88.88%> (+6.34%)	⬆️

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