Are public keys included in signatures? I can't easily and quickly determine from these wiki pages, 1 and 2, if the public key is included in the signed message.

Are public keys included in the signed message, or are they transmitted alongside the signatures, external to the signed message?
There are two answers to your question.

For a signed message, you can recover the public key if you have both the signature and the message that was used to create the signature.  The algorithm actually returns four possible keys, so the signature includes a header byte to identify which of the four should be used.  This is possible because we know which curve (secp256k1) is used by Bitcoin when it generates the signature.  If you want to see how this is done, look at recoverFromSignature() here

For a transaction, the public key is provided in the input script, the output script or a hashed script.  In the case of a multi-sig transaction, there are multiple signatures and multiple public keys.  There are also multiple ways to sign a transaction as determined by the signature hash type (a control byte added to the end of the signature).  If you want to see how this is done, look at checkSig() here