internal/pkg: streaming archive reader/writer

This is much more robust and efficient than the simple buffering implementation for larger files. Allocations happen almost exclusively in WalkDir.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/ir.go

@@ -21,7 +21,7 @@ import (
 const wordSize = 8
 
 // alignSize returns the padded size for aligning sz.
-func alignSize(sz int) int {
+func alignSize[T int | uint64](sz T) T {
 	return sz + (wordSize-(sz)%wordSize)%wordSize
 }