Where is it explicitly stated or otherwise infer-able that ammunition counts as a "weapon" for enchanting with special abilities (not just +X). In the SRD, it states that weapons are divided into two categories: melee or ranged. The only reference to ammunition counting as a "weapon" for the purposes of crafting it in any special way is special materials:
A weapon or a kind of ammunition may be made of an unusual material. Roll d%: 01-95 indicates that the item is of a standard sort, and 96-100 indicates that it is made of a special material.
Otherwise, the SRD (DMG) only talks about magical arrows with literal numeric enhancements. In the actual arrows entry, it states that they can be used as an improvised melee weapon, but we're erring on the reserved side of things for the purposes of this post where a DM will not allow you to have a chair, candle stick, etc. enchanted as a melee weapon.
So where can I find some examples of +1 Frost
arrows or +3 Magebane
maybe in a monster or sample character entry? Where can I find a more specific statement about ammunition being enchanted? I know that 99% of the CharOp community deduces that because it's not explicitly stated that arrows can't be enchanted with special abilities that they can, but let's assume for the duration of this thread that we're viewing things the other way around.
There may be a super simple answer right in the SRD that I'm missing, so sorry in advance.