Does I came hiking with you mean I arrived along with you by hiking, I have arrived for the purpose of hiking with you, or both?
Saying "I went hiking with you" would put it in the past tense such that the hiking is over, and the speaker is no longer in the location of the hike(s).
But as this is "I came hiking with you," the implication is that the speaker is still hiking on location with the person addressed. They are together, having already begun their hiking, and they are still hiking together. It would be like saying: "I came on this hike with you."
When come is linked to a participle of a verb of locomotion, the effect is to describe the manner of locomotion.
Consider the following:
He came walking up the street.
He came running up the street.
He came speeding up the street.
He came sashaying up the street.
He came crawling up the street.
He came stumbling up the street.
He came hiking up the street.
He came trekking up the street.
Of all of those verbs of locomotion, hiking and trekking stand out as unidiomatic or only marginally idiomatic because they don't refer primarily to manner of locomotion but, in the case of hiking, to the purpose of the locomotion, which is usually for fun and relaxation or exercise, or in the case of trekking, the primary meaning of the word involves the difficulties that must be endured along the way.
So, this common use of come + -ing form to describe manner of going works against your wish to have the phrase I came hiking with you mean "arrived along with you by hiking", as you put it. by-phrases refer to mode (by plane, by bus, by car, by taxi) which is not the same as manner. And hiking is primarily neither a mode of locomotion nor a manner of locomotion but locomotion with a specific purpose.
If we're talking about a past trip, I would normally say:
I went hiking with you
If I said:
I came hiking with you
this implies (for me), that it was really your hiking trip, and I joined it. That is, instead of the two of us planning the trip together, maybe you planned it with some friends, and I joined for a bit of it. Or it might suggest that we were hiking near where you lived, but I had to travel further to join.
Neither. The sentence "I came hiking with you" or any similar sentence in the form of "I came _______ with you" has no grammatical validity (other than in a sexual connotation...) unless you add context such as in "I came with you to the concert" which would imply that you were brought there rather than that you merely went together.
The sentence, "I came hiking with you."is addressed to the second person. Its like talking to your friend. Now came is the past form of come so the activity is already over. Sentences like, I've come for a hike with you, or I've come to join you for a hike, or I had come for a hike with you(for past tense) all mean that I had/have joined my friend for the activity of hiking. Notice the preposition "for". It signifies the intent of the duo to go for a hike. Now the sentences, "I came hiking with you" and "I went hiking with you" both don't use the word, 'for'. In that, there is ambiguity. However, "I went hiking with you", feel to mean that I had gone for the activity of hiking with you whereas, "I came hiking with you" tends to convey the meaning that I have arrived at some place with you via hiking. Similar sentences like, I came running with you, I came walking with you also convey similar meanings. It's like saying, I came(here) hiking with you.
Your question is does:
I came hiking with you
I arrived along with you by hiking
I have arrived for the purpose of hiking with you
The top answer correctly asserts that it means neither.
However, if the sentence was "I came, hiking with you" then, I'd argue, it means #1.
Without the comma "came hiking" is one action. With the comma the "came" and the "hiking" are no longer the same action. Instead it becomes two clauses.
The first: "I came".
That could be a stand alone sentence.
The second: "hiking with you"
This is a participle phrase that is describing the means by which you came.