fix(pstack): avoid canonical when clearer wording fits

[martinfrancois]

Avoid using canonical when a clearer word fits, such as "main checklist" instead of "canonical checklist". This change adds the word to the existing list in rule 26.

Before I asked Codex to avoid this word, it used it 132 times in 595,332 words. That is 2.22 uses per 10,000 words, compared with 0.158 in Python developer discussions from 2016 through 2018. Codex used it about 14.1 times as often in this comparison. All Codex text written after I introduced the preference on July 29, 2026, is excluded from both counts. The texts cover different subjects and years, so this does not prove that all AI tools use the word too often.

I compared the unchanged and changed skill in separate new Codex and Claude sessions. Each version produced 12 short texts per tool, across four sessions.

Tool	Unwanted uses before this change	After this change
Codex	3	0
Claude	4	0

I also checked that the change still allows valid uses. The writing requests did not supply the word canonical. With the changed skill, all six Ubuntu articles named Canonical, and all six answers asking for the standard SEO name of a preferred indexing address used "canonical URL". Each check ran three times per tool. The unchanged skill also passed these checks, so the change preserved this behavior.

These small tests do not guarantee the same results in every situation.

The change adds only one word.

[sherifattia]

The canonical solution to a canonical problem