This wiki article describes Kanada as both a sage and a philosopher. Was he a Rishi or a mere philosopher?
Yes. He was indeed a ṛṣi. But what kind of a ṛṣi was He? What was his expertise? From that wiki article you mentioned, it's obvious Kaṇāda pioneered the Vaiśeṣika vāda school, one of the Ṣaḍ Darśanas | 6 major Philosophies in Hinduism. Nevertheless, due to his (exalted) rank he was that of a seer, hence the prefixed title of « Maharṣi » to his name Kaṇāda i.e., He is addressed (and famous) as Maharṣi Kaṇāda.
Now, let me throw some light on the various level of ṛṣis. Ratna Kośa [A] & TriKāṇḍaŚeṣa (now extinct; from the whatever scattered quotes of them we have from the various vedic literatures) list 7 level of Ṛṣis which are being enumerated in their decreasing order of greatness as follows:
Deva-Born (= not of human origin):
① Brahmarṣi i.e., born from Brahmā e.g. Brahmarṣi Vasiṣṭha[B] [C]
② Devarṣi i.e., born out of Deva e.g. Devarṣi Nārada Muni
③ Maharṣi, the greatest of all ṛṣis who are of human race.
④ Paramarṣi, slightly below than Maharṣi
⑤ Kāṇḍarṣi, dealing with a certain Kāṇḍa — Chapter — of a Śāstra or Wing e.g., Jaimini (Mīmāṁsā propounder)
⑥ Śrutarṣi, one of the best preceptors of Śāstra
⑦ Rājarṣi, last and least in merit e. g., Viśvāmitra, Ṛtuparṇa, King Janaka
[A] Ratna Kośa -
sapta brahmarṣi devarṣi maharṣi paramarṣayaḥ ।
kāṇḍarṣiśca śrutarṣiśca rājarṣiśca kramāvarāḥ ॥
[B] Viṣṇu Purāṇa B1: 7.5
[C] Vāyu Purāṇa Vol. 1, 9.62