Remove never-read local variables (CodeQL java/local-variable-is-never-read)

[vharseko]

Summary

Resolves 16 of the 18 open CodeQL java/local-variable-is-never-read alerts by removing local variables that are assigned but never read. All removals are behavior-preserving — assignments whose right-hand side has an observable side effect are handled explicitly rather than dropped blindly.

Changes (12 files)

File	Module	Removed
ChunkedHtml.java	commons/doc-maven-plugin	chunkBaseDir (×2)
PngUtils.java	commons/doc-maven-plugin	absolutePath
AsyncHttpClientProvider.java	commons/http-framework	proxyStrategy
SyncHttpClientProvider.java	commons/http-framework	proxyStrategy
AsciiDoc.java	commons/rest/api-descriptor	symbol (unassigned decl)
IntegrityCheck.java	persistit/core	_totalPages (shadowing accumulator + its dead update)
AsciiDocIndex.java	persistit/doc	pSlash, displayText (×2)
FindFile.java	persistit/examples	model
SimpleDemo.java	persistit/examples	done
AdminUI.java	persistit/ui	iconName block
InspectorPanel.java	persistit/ui	iconName block
ManagementSlidingTableModel.java	persistit/ui	oldRowCount, lastUpdatedRow

Side-effect handling

• IntegrityCheck — the local _totalPages shadowed a field of the same name; both the declaration and its += …getNextAvailablePage() update are removed (the getter is pure and the field is managed separately), so the field's behaviour is unchanged.
• AdminUI / InspectorPanel — the iconName block calls st.nextToken(), but the StringTokenizer is discarded immediately afterwards, so removing the block is unobservable.

Intentionally left in place (2 alerts)

• BufferPool.reserve — a deliberate 1 MB allocation that is set to null inside catch (OutOfMemoryError) to free memory for error reporting; removing it would weaken OOM handling.
• ManagementTableModel.minWidth — its assignment consumes a StringTokenizer token whose position a later rendererName = st.nextToken() read depends on; removing it would shift token consumption.

Verification

Compiled commons/doc-maven-plugin, commons/http-framework/client-apache-async, commons/http-framework/client-apache-sync, commons/rest/api-descriptor, persistit/core, persistit/ui; plus javac for the AsciiDocIndex, FindFile and SimpleDemo persistit doc/example sources (not part of the Maven reactor).